Title

TINKER

Software Tools for Molecular Design

Version 4.2

June 2004

User's Guide Cover Illustration by Jay Nelson

Courtesy of Prof. R. T. Paine, Univ. of New Mexico

TINKER IS PROVIDED "AS IS" AND WITHOUT ANY WARRANTY EXPRESS OR IMPLIED. THE USER ASSUMES ALL RISKS OF USING THIS SOFTWARE. THERE IS NO CLAIM OF THE MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

YOU MAY MAKE COPIES OF TINKER FOR YOUR OWN USE, AND MODIFY THOSE COPIES. YOU MAY NOT DISTRIBUTE ANY MODIFIED SOURCE CODE OR DOCUMENTATION TO USERS AT ANY SITE OTHER THAN YOUR OWN. PLEASE SIGN AND RETURN THE TINKER LICENSE AGREEMENT IF YOU MAKE USE OF THIS SOFTWARE.

v4.2 6/04

TINKER

Software Tools for Molecular Design

Version 4.2 June 2004

Table of Contents Page

Introduction to the TINKER Package 5

Installing TINKER on your Computer 7

Types of Input & Output Files 10

Potential Energy Programs 13

Additional Utility Programs 19

Force Field Parameter Sets 23

Use of the Keyword Control File 31

Notes on Special Features & Methods 63

Descriptions of TINKER Routines 69

Contents of Common Block Variables 136

Index of Function & Subroutine Calls 163

Examples using the TINKER Package 189

Benchmark Results 191

Collaborators & Acknowledgments 195

References & Suggested Reading 197

1.	Introduction to the TINKER Package

Welcome to the TINKER molecular modeling package! TINKER is designed to be an easily used and flexible system of programs and routines for molecular mechanics and dynamics as well as other energy-based and structural manipulation calculations. It is intended to be modular enough to enable development of new computational methods and efficient enough to meet most production calculation needs. Rather than incorporating all the functionality in one monolithic program, TINKER provides a set of relatively small programs that interoperate to perform complex computations. New programs can be easily added by modelers with only limited programming experience. The series of major programs included in the distribution system perform the following core tasks:

(1) building protein and nucleic acid models from sequence

(2) energy minimization and structural optimization

(3) analysis of energy distribution within a structure

(4) molecular dynamics and stochastic dynamics

(5) simulated annealing with a choice of cooling schedules

(6) normal modes and vibrational frequencies

(7) conformational search and global optimization

(8) transition state location and conformational pathways

(9) fitting of energy parameters to crystal data

(10) distance geometry with pairwise metrization

(11) molecular volumes and surface areas

(12) free energy changes for structural mutations

(13) advanced algorithms based on potential smoothing

Many of the various energy minimization and molecular dynamics computations can be performed on full or partial structures, over Cartesian, internal or rigid body coordinates, and including a variety of boundary conditions and crystal cell types. Other programs are available to generate timing data and allow checking of potential function derivatives for coding errors. Special features are available to facilitate input and output of protein and nucleic acid structures. However, the basic core routines have no knowledge of biopolymer structure and can be used for general molecular systems.

Due to its emphasis on ease of modification, TINKER differs from many other currently available molecular modeling packages in that the user is expected to be willing to write simple ``front-end'' programs and make some alterations at the source code level. The main programs provided should be considered as templates for the users to change according to their wishes. All subroutines are internally documented and structured programming practices are adhered to throughout. The result, it is hoped, will be a calculational system which can be tailored to local needs and desires.

The core TINKER system consists of nearly 135,000 lines of source written entirely in a portable Fortran77 superset. Use is made of only some very common extensions that aid in writing highly structured code. The current version of the package has been ported to a wide range of computers with no or extremely minimal changes. Tested systems include: Red Hat Linux, Microsoft Windows 9X/NT/2000/XP, Apple OS9 and OSX, HP/Compaq/DEC Alphas under Tru64 Unix and OpenVMS, Hewlett-Packard, IBM, Silicon Graphics and Sun workstations under each vendor's Unix. At present, our new code is written on various Linux platforms, and occasionally tested for compatibility on various of the other machine and OS combinations listed above. At present, we are in the process of converting our primary development efforts from Fortran77 to a more modern Fortran dialect. A machine-translated C version of TINKER is currently available, and a hand-translated optimized C version of a previous TINKER release is available for inspection. Conversion to C or C++ is under consideration, but not being actively pursued at this time.

The basic design of the energy function engine used by the TINKER system allows usage of several different parameter sets. At present we are distributing parameters that implement AMBER ff94 and ff96, CHARMM19 and 27, MM2, MM3, OPLS-UA, OPLS-AA, Liam Dang's polarizable potentials, and our own AMOEBA (Atomic Multipole Optimized Energetics for Biomolecular Applications) parameters. In most cases, the source code separates the geometric manipulations needed for energy derivatives from the actual form of the energy function itself. Several other literature parameter sets are being considered for possible future development (ENCAD, MMFF-94, MM4, UFF, etc.), and many of the alternative potential function forms reported in the literature can be implemented directly or after minor code changes.

Much of the software in the TINKER package has been heavily used and well tested, but some modules are still in a fairly early stage of development. Further work on the TINKER system is planned in three main areas: (1) extension and improvement of the potential energy parameters including additional parameterization and testing of our polarizable multipole AMOEBA force field, (2) coding of new computational algorithms including additional methods for free energy determination, torsional Monte Carlo and molecular dynamics sampling, advanced methods for long range interactions, better transition state location, and further application of the potential smoothing paradigm, and (3) further development of Force Field Explorer, a Java-based GUI front-end to the TINKER programs that provides for calculation setup, launch and control as well as basic molecular visualization.

Questions and comments regarding the TINKER package, including suggestions for improvements and changes should be made to the author:

Professor Jay William Ponder

Biochemistry & Molecular Biophysics, Box 8231

Washington University School of Medicine

660 South Euclid Avenue

Saint Louis, MO 63110 U.S.A.

office: Center for Computational Biology, Room 208

phone: (314) 362-4195

fax: (314) 362-7183

email: ponder@dasher.wustl.edu

In addition, an Internet web site containing an online version of this User's Guide, the most recent distribution version of the full TINKER package and other useful information can be found at http://dasher.wustl.edu/tinker, the Home Page for the TINKER Molecular Modeling Package.

2.	Installing TINKER on your Computer

The TINKER package is distributed on the Internet via either the web site or the anonymous ftp account on dasher.wustl.edu with an IP number of 128.252.208.48. This node is a web and file server located in the Ponder lab at Washington University School of Medicine. The package is available via the web and standard browsers from the TINKER home page at http://dasher.wustl.edu/tinker/. Alternatively TINKER can be downloaded by logging into dasher.wustl.edu via anonymous ftp (Username: anonymous, Password: "your email address") and downloading the software from the /pub/tinker subdirectory. The complete TINKER distributions as well as individual files can be downloaded from this site.

The easiest way to get TINKER running on your machine is to use the self-extracting installation kit for either Linux, Windows, or Macintosh OS X 10.3. The installer will guide you through complete setup of TINKER and the Force Field Explorer (FFE) GUI, and perform all required configuration chores. The installer kits for the three supported systems are tinker4.2-linux.sh, tinker4.2-windows.exe and tinker4.2-macosx.sit. The Linux and Windows kits each contain a private copy of a Java and Java3D run-time environment for use with the package. The Macintosh version requires an OS X 10.3 (Panther) system for installation. The native Java implementation is used on Macs, and the Java3D package must be downloaded from Apple and installed prior to using TINKER with Force Field Explorer.

The TINKER package is also available as compressed Unix tar archives, Windows zip files, and as a complete set of uncompressed source and data files. Binaries are provided for machines running Windows 9X/ME/NT/2000/XP, Linux, and Apple Mac OS X. All of these executables are present in standard compressed formats as individual programs or as complete sets of executables. It is expected that other Unix users and PC users who need specially customized versions, will build binaries for their specific system. Sites with access to the Unix tar, compress and uncompress commands should simply obtain the archive file tinker.tar.Z. Alternatively, tinker.tar.gz and tinker.zip containing identical distributions compressed to GNU gzip and Windows ZIP format are also provided. If you choose to download individual files, you will need at a minimum the contents of the /doc, /source and /params subdirectories. Also required are the compile/build scripts from the subdirectory named for your machine type. Other areas contain test cases and examples, benchmark results, machine-translated C code, and the Force Field Explorer Java GUI for TINKER. The entire TINKER package, after building the executables, will require from about 40 to over 150 megabytes of disk space depending on the components installed and the use of shared libraries in the executables.

The documentation for the TINKER programs, including the guide you are currently reading, is located in the /pub/tinker/doc subdirectory. The documentation was prepared using the Applixware Words and Graphics programs. Portable versions of the documentation are provided as ascii text in .txt files and in Adobe Acrobat .pdf file formats. Please read and return by mail the TINKER license. In particular, we note that TINKER is not ``Open Source'' as users are prohibited from redistribution of original or modified TINKER source code or binaries to other parties. While our intent is to distribute the TINKER code to anyone who wants it, the Ponder Lab would like to remain the sole distribution site and keep track of researchers using the package. The returned license forms also help us justify further development of TINKER. When new modules and capabilities become available, and when the almost inevitable bugs are uncovered, we will attempt to notify those who have returned a license form. Finally, we remind you that this software is copyrighted, and ask that it not be redistributed in any form.

The compilation and building of the TINKER executables should be easy for most of the common workstation and PC class computers. We provide in the /make area a Unix-style Makefile that with some modification can be used to build TINKER on most Unix machines. As a simpler alternative to Makefiles for the Unix versions, we also provide machine-specific directories with three separate shell scripts to compile the source, build an object library, and link binary executables. Three similar command files are provided for Windows, Macintosh and Open VMS systems. Compilation on Unix workstations should use the vendor supplied Fortran compiler, if available. The public domain GNU g77 Fortran compiler available from http://gcc.gnu.org/ is also capable of building TINKER on Linux and other Unix-based machines. The Linux executables we provide are built with the Intel Fortran for Linux 8.0 compiler. The Portland Group (PGI) and Absoft ProFortran compilers have also been tested under Linux, both of which generate executables roughly comparable in speed to the Intel compiler. On Linux, the g77 executables tend to exhibit degraded performance compared with executables from commercial compilers. Some benchmark results are provided in a later section of this User's Guide For the Macintosh we distribute executables built under Apple OS X 10.3 with the GNU g77 compiler. TINKER also builds on the Macintosh using the Absoft ProFortran compiler. For PCs running Windows 9X/NT/2000/XP, the distributed TINKER executables are built under the Intel Fortran for Windows 8.0 compiler. Alternative Windows compilers such as Compaq Visual Fortran, Lahey/Fujitsu and The Portland Group compilers, and GNU g77 under Cygwin have been tested and shown to build TINKER correctly. Please see the README files in each of the machine-specific areas for further information.

The first step in building TINKER using the script files is to run the appropriate compile.make script for your operating system and compiler version. Next you must use a library.make script to create an archive of object code modules. Finally, run a link.make script to produce the complete set of TINKER executables. The executables can be renamed and moved to wherever you like by editing and running the ``rename'' script. These steps will produce executables that can run from the command line, but without the capability to interact with the FFE GUI. Building FFE-enabled TINKER executables involves replacing the sockets.f source file with sockets.c, and included the object from the C code in the TINKER object library. Then executables must be linked against Java libraries in addition to the usual resources. Sample compgui.make and linkgui.make scripts are provided for systems capable of building GUI-enabled executables.

Regardless of your target machine, only a few small pieces of code can possibly require attention prior to building. The first two are the system dependent time and date routines found in clock.f and calendar.f respectively. Next is the openend.f routine that facilitates appending data to the end of an existing disk file. Please uncomment the sections of these routines needed for your computer type. Version of these system dependent routines suitable for each system are also provided in the directory for each machine/OS type. The final set of possible source alterations are to the master array dimensions found in the include file sizes.i. The most basic limit is on the number of atoms allowed, ``maxatm''. This parameter can be set to 10000 or more on most workstations. Personal computers with minimal memory may need a lower limit, perhaps 1000 atoms, depending on available memory, swap space and other resources. A description of the other parameter values is contained in the header of the file. Note that in order to keep the code completely transparent, TINKER does not implement any sort of dynamic memory allocation or heap data structure. This requires that sizes.i dimensioning values be set at least as large as the biggest problem you intend to run. Obviously, you should not set the array sizes to unnecessarily large values, since this can tax your compute resources and may result in performance degradation or overt failure of the executables.

Specific questions about the building or use of the TINKER package should be directed to tinker@dasher.wustl.edu. TINKER related questions or comments of more general interest can be sent to the Computational Chemistry List (http://www.ccl.net/) run by Jan Labanowski at the University of Notre Dame. The TINKER developers monitor this list and will respond to the list or the individual poster as appropriate.

3.	Types of Input & Output Files

This section describes the basic file types used by the TINKER package. Let's say you wish to perform a calculation on a particular small organic molecule. Assume that the file name chosen for our input and output files is sample. Then all of the TINKER files will reside on the computer under the name sample.xxx where .xxx is any of the several extension types to be described below.

SAMPLE.XYZ

The .xyz file is the basic TINKER Cartesian coordinates file type. It contains a title line followed by one line for each atom in the structure. Each line contains: the sequential number within the structure, an atomic symbol or name, X-, Y-, and Z-coordinates, the force field atom type number of the atom, and a list of the atoms connected to the current atom. Except for programs whose basic operation is in torsional space, all TINKER calculations are done from some version of the .xyz format.

SAMPLE.INT

The .int file contains an internal coordinates representation of the molecular structure. It consists of a title line followed by one line for each atom in the structure. Each line contains: the sequential number within the structure, an atomic symbol or name, the force field atom type number of the atom, and internal coordinates in the usual Z-matrix format. For each atom the internal coordinates consist of a distance to some previously defined atom, and either two bond angles or a bond angle and a dihedral angle to previous atoms. The length, angle and dihedral definitions do not have to represent real bonded interactions. Following the last atom definition are two optional blank line separated sets of atom number pairs. The first list contains pairs of atoms that are covalently bonded, but whose bond length was not used as part of the atom definitions. These pairs are typically used to close ring structures. The second list contains ``bonds'' that are to be broken, i.e., pairs of atoms that are not covalently bonded, but which were used to define a distance in the atom definitions.

SAMPLE.KEY

The keyword parameter file always has the extension .key and is optionally present during TINKER calculations. It contains values for any of a wide variety of switches and parameters that are used to change the course of the computation from the default. The detailed contents of this file is explained in a latter section of this User's Guide. If a molecular system specific keyfile, in this case sample.key, is not present, the the TINKER program will look in the same directory for a generic file named tinker.key.

SAMPLE.DYN

The .dyn file contains values needed to restart a molecular or stochastic dynamics computation. It stores the current position, current velocity and current and previous accelerations for each atom, as well as the size and shape of any periodic box or crystal unit cell. This information can be used to start a new dynamics run from the final state of a previous run. Upon startup, the dynamics programs always check for the presence of a .dyn file and make use of it whenever possible. The .dyn file is updated concurrent with the saving of a new dynamics trajectory snapshot.

SAMPLE.END

The .end file type provides a mechanism to gracefully stop a running TINKER calculation. At appropriate checkpoints during a calculation, TINKER will test for the presence of a sample.end file, and if found will terminate the calculation after updating the output. The .end file can be created at any time during a computation, and will be detected when the next checkpoint is reached. The file may be of zero size, and its contents are unimportant. In the current version of TINKER, the .end mechanism is only available within dynamics-based programs.

SAMPLE.001, SAMPLE.002, ....

Several types of computations produce files containing a three or more digit extension (.001 as shown; or .002, .137, .5678, etc.). These are referred to as cycle files, and are used to store various types of output structures. The cycle files from a given computation are identical in internal structure to either the .xyz or .int files described above. For example, the vibrational analysis program can save the tenth normal mode in sample.010. A molecular dynamics-based program might save its tenth 0.1 picosecond frame (or an energy minimizer its tenth partially minimized intermediate) in a file of the same name.

SAMPLE.LOG

The Force Field Explorer interface to TINKER saves results of all calculations launched from the GUI to a log file with the .log suffix. Any output that would normally be directed to the screen after starting a program from the command line is appended to this log file by Force Field Explorer.

SAMPLE.ARC

A TINKER archive file is simply a series of .xyz Cartesian coordinate files appended together one after another. This file can be used to condense the results from intermediate stages of an optimization, frames from a molecular dynamics trajectory, or set of normal mode vibrations into a single file for storage. TINKER archive files can be displayed as ``movies'' by the Force Field Explorer modeling program.

SAMPLE.PDB

This file type contains coordinate information in the PDB format developed by the Brookhaven Protein Data Bank for deposition of model structures based on macromolecular X-ray diffraction and NMR data. Although TINKER itself does not use .pdb files directly for input/output, auxiliary programs are provided with the system for interconverting .pdb files with the .xyz format described above.

SAMPLE.SEQ

This file type contains the primary sequence of a biopolymer in the standard one-letter code with 50 residues per line. The .seq file for a biopolymer is generated automatically when a PDB file is converted to TINKER .xyz format or when using the PROTEIN or NUCLEIC programs to build a structure from sequence It is required for the reverse conversion of a TINKER file back to PDB format..

SAMPLE.FRAC

The fractional coordinates corresponding to the asymmetric unit of a crystal unit cell are stored in the .frac file. The internal format of this file is identical to the .xyz file; except that the coordinates are fractional instead of in Angstrom units.

SAMPLE.XMOL

The ARCHIVE program has the option of converting a series of .xyz cycle files into an XMakemol XYZ file. These files can be displayed as a movie using the XMakemol display program. Note that the .xmol file format does not contain TINKER atom type information, so it is not possible to convert an .xmol file back into a TINKER .xyz file.

SAMPLE.CAR

The ARCHIVE program has the option of converting a series of .xyz cycle files into an Accelerys InsightII coordinate archive file. These files can be displayed as a movie using the InsightII display program. Note that the .car file format does not contain TINKER atom type information, so it is not possible to convert a .car file back into a TINKER .XYZ file.

PARAMETER FILES

The potential energy parameter files distributed with the TINKER package all end in the extension .prm, although this is not required by the programs themselves. Each of these files contains a definition of the potential energy functional forms for that force field as well as values for individual energy parameters. For example, the mm3pro.prm file contains the energy parameters and definitions needed for a protein-specific version of the MM3 force field.

4.	Potential Energy Programs

This section of the manual contains a brief description of each of the TINKER potential energy programs. A detailed example showing how to run each program is included in a later section. The programs listed below are all part of the main, supported distribution. Additional source code for various unsupported programs can be found in the /other directory of the TINKER distribution.

ALCHEMY

A simple program to perform very basic free energy perturbation calculations. This program is provided mostly for demonstration purposes. For example, we use ALCHEMY in a molecular modeling course laboratory exercise to perform such classic mutations as chloride to bromide and ethane to methanol in water. The present version uses the perturbation formula and windowing with an explicit mapping of atoms involved in the mutation (``AMBER''-style), instead of thermodynamic integration and independent freely propagating groups of mutated atoms (``CHARMM''-style). Some of the code specific to this program is limited to the AMBER and OPLS potential functional forms, but could be easily generalized to handle other potentials. A more general and sophisticated version is currently under development.

ANALYZE

Provides information about a specific molecular structure. The program will ask for the name of a structure file, which must be in the TINKER .xyz file format, and the type of analysis desired. Options allow output of: (1) total potential energy of the system, (2) breakdown of the energy by potential function type or over individual atoms, (3) computation of the total dipole moment and its components, moments of inertia and radius of gyration, (4) listing of the parameters used to compute selected interaction energies, (5) energies associated with specified individual interactions.

ANNEAL

Performs a molecular dynamics simulated annealing computation. The program starts from a specified input molecular structure in TINKER .xyz format. The trajectory is updated using either a modified Beeman or a velocity Verlet integration method. The annealing protocol is implemented by allowing smooth changes between starting and final values of the system temperature via the Groningen method of coupling to an external bath. The scaling can be linear or sigmoidal in nature. In addition, parameters such as cutoff distance can be transformed along with the temperature. The user must input the desired number of dynamics steps for both the equilibration and cooling phases, a time interval for the dynamics steps, and an interval between coordinate/trajectory saves. All saved coordinate sets along the trajectory are placed in sequentially numbered cycle files.

DYNAMIC

Performs a molecular dynamics (MD) or stochastic dynamics (SD) computation. Starts either from a specified input molecular structure (an .xyz file) or from a structure-velocity-acceleration set saved from a previous dynamics trajectory (a restart from a .dyn file). MD trajectories are propagated using either a modified Beeman or a velocity Verlet integration method. SD is implemented via our own derivation of a velocity Verlet-based algorithm. In addition the program can perform full crystal calculations, and can operate in constant energy mode or with maintenance of a desired temperature and/or pressure using the Groningen method of coupling to external baths. The user must input the desired number of dynamics steps, a time interval for the dynamics steps, and an interval between coordinate/trajectory saves. Coordinate sets along the trajectory can be saved as sequentially numbered cycle files or directly to a TINKER archive .arc file. At the same time that a point along the trajectory is saved, the complete information needed to restart the trajectory from that point is updated and stored in the .dyn file.

GDA

A program to implement Straub's Gaussian Density Annealing algorithm over an effective series of analytically smoothed potential energy surfaces. This method can be viewed as an extended stochastic version of the diffusion equation method of Scheraga, et al., and also has many similar features to the TINKER Potential Smoothing and Search (PSS) series of programs. The current version of GDA is similar to but does not exactly reproduce Straub's published method and is limited to argon clusters and other simple systems involving only van der Waals interactions; further modification and development of this code is currently underway in the Ponder research group. As with other programs involving potential smoothing, GDA currently requires use of the smooth.prm force field parameters.

MINIMIZE

The MINIMIZE program performs a limited memory L-BFGS minimization of an input structure over Cartesian coordinates using a modified version of the algorithm of Jorge Nocedal. The method requires only the potential energy and gradient at each step along the minimization pathway. It requires storage space proportional to the number of atoms in the structure. The MINIMIZE procedure is recommended for preliminary minimization of trial structures to an rms gradient of 1.0 to 0.1 kcal/mole/Å. It has a relatively fast cycle time and is tolerant of poor initial structures, but converges in a slow, linear fashion near the minimum. The user supplies the name of the TINKER .xyz coordinates file and a target rms gradient value at which the minimization will terminate. Output consists of minimization statistics written to the screen or redirected to an output file, and the new coordinates written to updated .xyz files or to cycle files.

MINIROT

The MINIROT program uses the same limited memory L-BFGS method as MINIMIZE, but performs the computation in terms of dihedral angles instead of Cartesian coordinates. Output is saved in an updated .int file or in cycle files.

MINRIGID

The MINRIGID program is similar to MINIMIZE except that it operates on rigid bodies starting from a TINKER .xyz coordinate file and the rigid body group definitions found in the corresponding .key file. Output is saved in an updated .xyz file or in cycle files.

MONTE

The MONTE program implements the Monte Carlo Minimization algorithm developed by Harold Scheraga's group and others. The procedure takes Monte Carlo steps for either a single atom or a single torsional angle, then performs a minimization before application of the Metropolis sampling method. This results in effective sampling of a modified potential surface where the only possible energy levels are those of local minima on the original surface. The program can be easily modified to elaborate on the available move set.

NEWTON

A truncated Newton minimization method which requires potential energy, gradient and Hessian information. This procedure has significant advantages over standard Newton methods, and is able to minimize very large structures completely. Several options are provided with respect to minimization method and preconditioning of the Newton equations. The default options are recommended unless the user is familiar with the math involved. This program operates in Cartesian coordinate space and is fairly tolerant of poor input structures. Typical algorithm iteration times are longer than with nonlinear conjugate gradient or variable metric methods, but many fewer iterations are required for complete minimization. NEWTON is usually the best choice for minimizations to the 0.01 to 0.000001 kcal/mole/Å level of rms gradient convergence. Tests for directions of negative curvature can be removed, allowing NEWTON to be used for optimization to conformational transition state structures (this only works if the starting point is very close to the transition state). Input consists of a TINKER .xyz coordinates file; output is an updated set of minimized coordinates and minimization statistics.

NEWTROT

The NEWTROT program is similar to NEWTON except that it requires a .int file as input and then operates in terms of dihedral angles as the minimization variables. Since the dihedral space Hessian matrix of an arbitrary structure is often indefinite, this method will often not perform as well as the other, simpler dihedral angle based minimizers.

OPTIMIZE

The OPTIMIZE program performs a optimally conditioned variable metric minimization of an input structure over Cartesian coordinates using an algorithm due to William Davidon. The method does not perform line searches, but requires computation of energies and gradients as well as storage for an estimate of the inverse Hessian matrix. The program operates on Cartesian coordinates from a TINKER .xyz file. OPTIMIZE will typically converge somewhat faster and more completely than MINIMIZE. However, the need to store and manipulate a full inverse Hessian estimate limits its use to structures containing less than a few hundred atoms on workstation class machines. As with the other minimizers, OPTIMIZE needs input coordinates and an rms gradient cutoff criterion. The output coordinates are saved in updated .xyz files or as cycle files.

OPTIROT

The OPTIROT program is similar to OPTIMIZE except that it operates on dihedral angles starting from a TINKER .int internal coordinate file. This program is usually the preferred method for most dihedral angle optimization problems since Truncated Newton methods appear, in our hands, to lose some of their efficacy in moving from Cartesian to torsional coordinates.

OPTRIGID

The OPTRIGID program is similar to OPTIMIZE except that it operates on rigid bodies starting from a TINKER .xyz coordinate file and the rigid body atom group definitions found in the corresponding .key file. Output is saved in an updated .xyz file or in cycle files.

PATH

A program that implements a variant of Elber's Lagrangian multiplier-based reaction path following algorithm. The program takes as input a pair of structural minima as TINKER .xyz files, and then generates a user specified number of points along a path through conformational space connecting the input structures. The intermediate structures are output as TINKER cycle files, and the higher energy intermediates can be used as input to a Newton-based optimization to locate conformational transition states.

PSS

Implements our version of a potential smoothing and search algorithm for the global optimization of molecular conformation. An initial structure in .xyz format is first minimized in Cartesian coordinates on a series of increasingly smoothed potential energy surfaces. Then the smoothing procedure is reversed with minimization on each successive surface starting from the coordinates of the minimum on the previous surface. A local search procedure is used during the backtracking to explore for alternative minima better than the one found during the current minimization. The final result is usually a very low energy conformation or, in favorable cases, the global energy minimum conformation. The minimum energy coordinate sets found on each surface during both the forward smoothing and backtracking procedures are placed in sequentially numbered cycle files.

PSSRIGID

This program implements the potential smoothing and search method as described above for the PSS program, but performs the computation in terms of keyfile-defined rigid body atom groups instead of Cartesian coordinates. Output is saved in numbered cycle files with the .xyz file format.

PSSROT

This program implements the potential smoothing and search method as described above for the PSS program, but performs the computation in terms of a set of user-specified dihedral angles instead of Cartesian coordinates. Output is saved in numbered cycle files with the .int file format.

SADDLE

A program for the location of a conformational transition state between two potential energy minima. SADDLE uses a conglomeration of ideas from the Bell-Crighton quadratic path and the Halgren-Lipscomb synchronous transit methods. The basic idea is to perform a nonlinear conjugate gradient optimization in a subspace orthogonal to a suitably defined reaction coordinate. The program requires as input the coordinates (TINKER .xyz files) of the two minima and an rms gradient convergence criterion for the optimization. The current estimate of the transition state structure is written to the file TSTATE.XYZ. Crude transition state structures generated by SADDLE can sometimes be refined using the NEWTON program. Optionally, a scan of the interconversion pathway can be made at each major iteration.

SCAN

A program for general conformational search of an entire potential energy surface via a basin hopping method. The program takes as input a TINKER .xyz coordinates file which is then minimized to find the first local minimum for a search list. A series of activations along various normal modes from this initial minimum are used as seed points for additional minimizations. Whenever a previously unknown local minimum is located it is added to the search list. When all minima on the search list have been subjected to the normal mode activation without locating additional new minima, the program terminates. The individual local minima are written to cycle files as they are discovered. While the SCAN program can be used on standard undeformed potential energy surfaces, we have found it to be most useful for quickly ``scanning'' a smoothed energy surface to enumerate the major basins of attraction spaning the entire surface.

SNIFFER

A program that implements the Sniffer global optimization algorithm of Butler and Slaminka, a discrete version of Griewank's global search trajectory method. The program takes an input TINKER .xyz coordinates file and shakes it vigorously via a modified dynamics trajectory before, hopefully, settling into a low lying minimum. Some trial and error is often required as the current implementation is sensitive to various parameters and tolerances that govern the computation. At present, these parameters are not user accessible, and must be altered in the source code. However, this method can do a good job of quickly optimizing conformation within a limited range of convergence.

TESTGRAD

The TESTGRAD program computes and compares the analytical and numerical first derivatives (i.e., the gradient vector) of the potential energy for a Cartesian coordinate input structure. The output can be used to test or debug the current potential or any added user defined energy terms.

TESTHESS

The TESTHESS program computes and compares the analytical and numerical second derivatives (i.e., the Hessian matrix) of the potential energy for a Cartesian coordinate input structure. The output can be used to test or debug the current potential or any added user defined energy terms.

TESTLIGHT

A program to compare the efficiency of different nonbonded neighbor methods for the current molecular system. The program times the computation of energy and gradient for the van der Waals and charge-charge electrostatic potential terms using a simple double loop over all interactions and using the Method of Lights algorithm to select neighbors. The results can be used to decide whether the Method of Lights has any CPU time advantage for the current structure. Both methods should give exactly the same answer in all cases, since the identical individual interactions are computed by both methods. The default double loop method is faster when cutoffs are not used, or when the cutoff sphere contains about half or more of the total system of unit cell. In cases where the cutoff sphere is much smaller than the system size, the Method of Lights can be much faster since it avoids unnecessary calculation of distances beyond the cutoff range.

TESTROT

The TESTROT program computes and compares the analytical and numerical first derivatives (i.e., the gradient vector) of the potential energy with respect to dihedral angles. Input is a TINKER .int internal coordinate file. The output can be used to test or debug the current potential functions or any added user defined energy terms.

TIMER

A simple program to provide timing statistics for energy function calls within the TINKER package. TIMER requires an input .xyz file and outputs the CPU time (wall clock time on some machine types) needed to perform a specified number of energy, gradient and Hessian evaluations.

TIMEROT

This program is similar to TIMER, only it operates over dihedral angles via input of a TINKER .int internal coordinate file. In the current version, the torsional Hessian is computed numerically from the analytical torsional gradient.

VIBRATE

A program to perform vibrational analysis by computing and diagonalizing the full Hessian matrix (i.e., the second partial derivatives) for an input structure (a TINKER .xyz file). Eigenvalues and eigenvectors of the mass weighted Hessian (i.e., the vibrational frequencies and normal modes) are also calculated. Structures corresponding to individual normal mode motions can be saved in cycle files.

VIBROT

The program VIBROT forms the torsional Hessian matrix via numerical differentiation of the analytical torsional gradient. The Hessian is then diagonalized and the eigenvalues are output. The present version does not compute the kinetic energy matrix elements needed to convert the Hessian into the torsional normal modes; this will be added in a later version. The required input is a TINKER .int internal coordinate file.

XTALFIT

The XTALFIT program is of use in the automated fitting of potential parameters to crystal structure and thermodynamic data. XTALFIT takes as input several crystal structures (TINKER .xyz files with unit cell parameters in corresponding keyfiles) as well as information on lattice energies and dipole moments of monomers. The current version uses a nonlinear least squares optimization to fit van der Waals and electrostatic parameters to the input data. Bounds can be placed on the values of the optimization parameters.

XTALMIN

A program to perform full crystal minimizations. The program takes as input the structure coordinates and unit cell lattice parameters. It then alternates cycles of Newton-style optimization of the structure and conjugate gradient optimization of the crystal lattice parameters. This alternating minimization is slower than more direct optimization of all parameters at once, but is somewhat more robust in our hands. The symmetry of the original crystal is not enforced, so interconversion of crystal forms may be observed in some cases.

5.	Additional Utility Programs

This section of the manual contains a brief description of each of the TINKER structure manipulation, geometric calculation and auxiliary programs. A detailed example showing how to run each program is included in a later section. The programs listed below are all part of the main, supported distribution. Additional source code for various unsupported programs can be found in the /other directory of the TINKER distribution.

ARCHIVE

A program for concatenating TINKER cycle files into a single archive file; useful for storing the intermediate results of minimizations, dynamics trajectories, and so on. The archive file can be written in TINKER format, or in formats usable with MSI's InsightII (their CAR file with .msi extension) or with XMakemol (their file format with .xmol extension). Only active atoms are written into the InsightII and XMakemol output files, allowing display of partial structures. The program can also extract individual cycle files from a TINKER archive.

CORRELATE

A program to compute time correlation functions from collections of TINKER cycle files. Its use requires a user supplied function property that computes the value of the property for which a time correlation is desired for two input structures. A sample routine is supplied that computes either a velocity autocorrelation function or an rms structural superposition as a function of time. The main body of the program organizes the overall computation in an efficient manner and outputs the final time correlation function.

CRYSTAL

A program for the manipulation of crystal structures including interconversion of fractional and Cartesian coordinates, generation of the unit cell from an asymmetric unit, and building of a crystalline block of specified size via replication of a single unit cell. The present version can handle about 25 of the most common space groups, others can easily be added as needed by modification of the routine symmetry.

DIFFUSE

A program to compute the self-diffusion constant for a homogeneous liquid via the Einstein equation. A previously saved dynamics trajectory is read in and ``unfolded'' to reverse translation of molecules due to use of periodic boundary conditions. The average motion over all molecules is then used to compute the self-diffusion constant. While the current program assumes a homogeneous system, it should be easy to modify the code to handle diffusion of individual molecules or other desired effects.

DISTGEOM

A program to perform distance geometry calculations using variations on the classic metric matrix method. A user specified number of structures consistent with keyfile input distance and dihedral restraints is generated. Bond length and angle restraints are derived from the input structure. Trial distances between the triangle smoothed lower and upper bounds can be chosen via any of several metrization methods, including a very effective partial random pairwise scheme. The correct radius of gyration of the structure is automatically maintained by choosing trial distances from Gaussian distributions of appropriate mean and width. The initial embedded structures can be further refined against a geometric restraint-only potential using either a sequential minimization protocol or simulated annealing.

DOCUMENT

The DOCUMENT program is provided as a minimal listing and documentation tool. It operates on the TINKER source code, either individual files or the complete source listing produced by the command script listing.make, to generate lists of routines, common blocks or valid keywords. In addition, the program has the ability to output a formatted parameter listing from the standard TINKER parameter files.

INTEDIT

A program to allow interactive inspection and alteration of the internal coordinate definitions and values of a TINKER structure. If the structure is altered, the user has the option to write out a new internal coordinates file upon exit.

INTXYZ

A program to convert a TINKER .int internal coordinates formatted file into a TINKER .xyz Cartesian coordinates formatted file.

NUCLEIC

A program for automated building of nucleic acid structures. Upon interactive input of a nucleotide sequence with optional phosphate backbone angles, the program builds internal and Cartesian coordinates. Standard bond lengths and angles are used. Both DNA and RNA sequences are supported as are A-, B- and Z-form structures. Double helixes of complementary sequence can be automatically constructed via a rigid docking of individual strands.

PDBXYZ

A program for converting a Brookhaven Protein Data Bank file (a PDB file) into a TINKER .xyz Cartesian coordinate file. If the PDB file contains only protein/peptide amino acid residues, then standard protein connectivity is assumed, and transferred to the .xyz file. For non-protein portions of the PDB file, atom connectivity is determined by the program based on interatomic distances. The program also has the ability to add or remove hydrogen atoms from a protein as required by the force field specified during the computation.

POLARIZE

A program for computing molecular polarizability from an atom-based distributed model of polarizability. A damped interaction model due to Thole is optionally via keyfile settings. A TINKER .xyz file is required as input. The output consists of the overall polarizability tensor in the global coordinates and its eigenvalues.

PRMEDIT

A program for formatting and renumbering TINKER force field parameter files. When atom types or classes are added to a parameter file, this utility program has the ability to renumber all the atom records sequentially, and alter type and class numbers in all other parameter entries to maintain consistency.

PROTEIN

A program for automated building of peptide and protein structures. Upon interactive input of an amino acid sequence with optional phi/psi/omega/chi angles, D/L chirality, etc., the program builds internal and Cartesian coordinates. Standard bond lengths and angles are assumed for the peptide. The program will optionally convert the structure to a cyclic peptide, or add either or both N- and C-terminal capping groups. Atom type numbers are automatically assigned for the specified force field. The final coordinates and a sequence file are produced as the output.

RADIAL

A program to compute the pair radial distribution function between two atom types. The user supplies the two atom names for which the distribution function is to be computed, and the width of the distance bins for data analysis. A previously saved dynamics trajectory is read as input. The raw radial distribution and a spline smoothed version are then output from zero to a distance equal to half the minimum periodic box dimension. The atom names are matched to the atom name column of the TINKER .xyz file, independent of atom type.

SPACEFILL

A program to compute the volume and surface areas of molecules. Using a modified version of Connolly's original analytical description of the molecular surface, the program determines either the van der Waals, accessible or molecular (contact/reentrant) volume and surface area. Both surface area and volume are broken down into their geometric components, and surface area is decomposed into the convex contribution for each individual atom. The probe radius is input as a user option, and atomic radii can be set via the keyword file. If TINKER archive files are used as input, the program will compute the volume and surface area of each structure in the input file.

SPECTRUM

A program to compute a power spectrum from velocity autocorrelation data. As input, this program requires a velocity autocorrelation function as produced by the CORRELATE program. This data, along with a user input time step, are Fourier transformed to generate the spectral intensities over a wavelength range. The result is a power spectrum, and the positions of the bands are those predicted for an infrared or Raman spectrum. However, the data is not weighted by molecular dipole moment derivatives as would be required to produce correct IR intensities.

SUPERPOSE

A program to superimpose two molecular structures in 3-dimensions. A variety of options for input of the atom sets to be used during the superposition are presented interactively to the user. The superposition can be mass-weighted if desired, and the coordinates of the second structure superimposed on the first structure are optionally output. If TINKER archive files are used as input, the program will compute all pairwise superpositions between structures in the input files.

SYBYLXYZ

A program for converting a TRIPOS Sybyl MOL2 file into a TINKER .xyz Cartesian coordinate file. The current version of the program does not attempt to convert the Sybyl atoms types into the active TINKER force field types, i.e., all atoms types are simply set to zero.

TVIEW

This is a molecule viewing program derived from the well-know Rasmol program of Roger Sayle. TVIEW is modified to remove most of the protein-specific options and to directly read the TINKER .xyz file format. The original RasMol program has been altered to allow selection and specification by atoms instead of residues. We hope to provide additional functionality in future versions of TVIEW, especially the ability to animate the viewing of sequences of coordinate snapshots from a minimization or dynamic trajectory.

XYZEDIT

A program that performs and of a variety of manipulations on an input TINKER .xyz Cartesian coordinates formatted file. The present version of the program has the following interactively selectable options: (1) Offset the Numbers of the Current Atoms, (2) Deletion of Individual Specified Atoms, (3) Deletion of Specified Types of Atoms, (4) Deletion of Atoms outside Cutoff Range, (5) Insertion of Individual Specified Atoms, (6) Replace Old Atom Type with a New Type, (7) Assign Connectivities based on Distance, (8) Convert Units from Bohrs to Angstroms, (9) Invert thru Origin to give Mirror Image, (10) Translate Center of Mass to the Origin, (11) Translate a Specified Atom to the Origin, (12) Translate and Rotate to Inertial Frame, (13) Move to Specified Rigid Body Coordinates, (14) Create and Fill a Periodic Boundary Box, (15) Soak Current Molecule in Box of Solvent, (16) Append another XYZ file to Current One. In most cases, multiply options can be applied sequentially to an input file. At the end of the editing process, a new version of the original .xyz file is written as output.

XYZINT

A program for converting a TINKER .xyz Cartesian coordinate formatted file into a TINKER .int internal coordinates formatted file. This program can optionally use an existing internal coordinates file as a template for the connectivity information.

XYZPDB

A program for converting a TINKER .xyz Cartesian coordinate file into a Brookhaven Protein Data Bank file (a PDB file).

XYZSYBYL

A program to convert a TINKER .xyz Cartesian coordinates file into a TRIPOS Sybyl MOL2 file. The conversion generates only the MOLECULE, ATOM, BOND and SUBSTRUCTURE record type in the MOL2 file. Generic Sybyl atom types are used in most cases; while these atom types may need to be altered in some cases, Sybyl is usually able to correctly display the resulting MOL2 file.

6.	Force Field Parameter Sets

The TINKER package is distributed with several force field parameter sets, implementing a selection of widely used literature force fields as well as the TINKER force field currently under construction in the Ponder lab. We try to exactly reproduce the intent of the original authors of our distributed, third-party force fields. In all cases the parameter sets have been validated against literature reports, results provided by the original developers, or calculations made with the authentic programs. With the few exceptions noted below, TINKER calculations can be treated as authentic results from the genuine force fields. A brief description of each parameter set, including some still in preparation and not distributed with the current version, is provided below with lead literature references for the force field:

AMOEBA.PRM

Parameters for the AMOEBA polarizable atomic multipole force field. As of the current TINKER release, we have completed parametrization for a number of ions and small organic molecules. For further information, or if you are interested in developing or testing parameters for other small molecules, please contact the Ponder lab.

P. Ren and J. W. Ponder, A Consistent Treatment of Inter- and Intramolecular Polarization in Molecular Mechanics Calculations, J. Comput. Chem., 23, 1497-1506 (2002)

P. Ren and J. W. Ponder, Polarizable Atomic Multipole Water Model for Molecular Mechanics Simulation, J. Phys. Chem. B, 107, 5933-5947 (2003)

P. Ren and J. W. Ponder, Ion Solvation Thermodynamics from Simulation with a Polarizable Force Field, A. Grossfield, J. Am. Chem. Soc., 125, 15671-15682 (2003)

AMOEBAPRO.PRM

Preliminary protein parameters for the AMOEBA polarizable atomic multipole force field. While the distributed parameters are still subject to minor alteration as we continue validation, they are now stable enough for other groups to begin using them. For further information, or if you are interested in testing the protein parameter set, please contact the Ponder lab.

J. W. Ponder and D. A. Case, Force Fields for Protein Simulation, Adv. Prot. Chem., 66, 27-85 (2003)

P. Ren and J. W. Ponder, Polarizable Atomic Multipole-based Potential for Proteins: Model and Parameterization, in preparation

AMBER94.PRM

AMBER ff94 parameters for proteins and nucleic acids. Note that with their ``Cornell'' force field, the Kollman group has devised separate, fully independent partial charge values for each of the N- and C-terminal amino acid residues. At present, the terminal residue charges for TINKER's version maintain the correct formal charge, but redistributed somewhat at the alpha carbon atoms from the original Kollman group values. The total magnitude of the redistribution is less than 0.01 electrons in most cases.

W. D. Cornell, P. Cieplak, C. I. Bayly, I. R. Gould, K. M. Merz, Jr., D. M. Ferguson, D. C. Spellmeyer, T. Fox, J. W. Caldwell and P. A. Kollman, A Second Generation Force Field for the Simulation of Proteins, Nucleic Acids, and Organic Molecules, J. Am. Chem. Soc., 117, 5179-5197 (1995) [ff94]

G. Moyna, H. J. Williams, R. J. Nachman and A. I. Scott, Conformation in Solution and Dynamics of a Structurally Constrained Linear Insect Kinin Pentapeptide Analogue, Biopolymers, 49, 403-413 (1999) [AIB charges]

W. S. Ross and C. C. Hardin, Ion-Induced Stabilization of the G-DNA Quadruplex: Free Energy Perturbation Studies, J. Am. Chem. Soc., 116, 4363-4366 (1994) [alkali metal ions]

J. Aqvist, Ion-Water Interaction Potentials Derived from Free Energy Perturbation Simulations, J. Phys. Chem., 94, 8021-8024, 1990 [alkaline earth Ions, radii adapted for Amber combining rule]

Current force field parameter values and suggested procedures for development of parameters for additional molecules are available from the Amber web site in the Case lab at Scripps, http://amber.scripps.edu/

AMBER96.PRM

AMBER ff96 parameters for proteins and nucleic acids. The only change from the ff94 parameter set is in the torsional parameters for the protein phi/psi angles. These values were altered to give better agreement with changes of ff96 with LMP2 QM results from the Friesner lab on alanine dipeptide and tetrapeptide.

P. Kollman, R. Dixon, W. Cornell, T. Fox, C. Chipot and A. Pohorille, The Development/ Application of a 'Minimalist' Organic/Biochemical Molecular Mechanic Force Field using a Combination of ab Initio Calculations and Experimental Data, in Computer Simulation of Biomolecular Systems, W. F. van Gunsteren, P. K. Weiner, A. J. Wilkinson, eds., Volume 3, 83-96 (1997) [ff96]

AMBER98.PRM

AMBER ff98 parameters for proteins and nucleic acids. The only change from the ff94 parameter set is in the glycosidic torsional parameters that control sugar pucker.

T. E. Cheatham III, P. Cieplak and P. A. Kollman, A Modified Version of the Cornell et al. Force Field with Improved Sugar Pucker Phases and Helical Repeat, J. Biomol. Struct. Dyn., 16, 845-862 (1999)

AMBER99.PRM

AMBER ff99 parameters for proteins and nucleic acids. The original partial charges from the ff94 parameter set are retained, but many of the bond, angle and torsional parameters have been revised to provide better general agreement with experiment.

J. Wang, P. Cieplak and P. A. Kollman, How Well Does a Restrained Electrostatic Potential (RESP) Model Perform in Calcluating Conformational Energies of Organic and Biological Molecules?, J. Comput. Chem., 21, 1049-1074 (2000)

CHARMM19.PRM

CHARMM19 united-atom parameters for proteins. The nucleic acid parameter are not yet implemented. There are some differences between authentic CHARMM19 and the TINKER version due to replacement of CHARMM impropers by torsions for cases that involve atoms not bonded to the trigonal atom and TINKER's use of all possible torsions across a bond instead of a single torsion per bond.

E. Neria, S. Fischer and M. Karplus, Simulation of Activation Free Energies in Molecular Systems, J. Chem. Phys., 105, 1902-1921 (1996)

L. Nilsson and M. Karplus, Empirical Energy Functions for Energy Minimizations and Dynamics of Nucleic Acids, J. Comput. Chem., 7, 591-616 (1986)

W. E. Reiher III, Theoretical Studies of Hydrogen Bonding, Ph.D. Thesis, Department of Chemistry, Harvard University, Cambridge, MA, 1985

CHARMM27.PRM

CHARMM27 all-atom parameters for proteins and lipids. Most of the nucleic acid and small model compound parameters are not yet implemented. We plan to provide these additional parameters in due course.

N. Foloppe and A. D. MacKerell, Jr., All-Atom Empirical Force Field for Nucleic Acids: 1) Parameter Optimization Based on Small Molecule and Condensed Phase Macromolecular Target Data, J. Comput. Chem., 21, 86-104 (2000) [CHARMM27]

N. Banavali and A. D. MacKerell, Jr., All-Atom Empirical Force Field for Nucleic Acids: 2) Application to Molecular Dynamics Simulations of DNA and RNA in Solution, J. Comput. Chem., 21, 105-120 (2000)

A. D. MacKerrell, Jr., et al., All-Atom Empirical Potential for Molecular Modeling and Dynamics Studies of Proteins, J. Phys. Chem. B, 102, 3586-3616 (1998) [CHARMM22]

A. D. MacKerell, Jr., J. Wiorkeiwicz-Kuczera and M. Karplus, An All-Atom Empirical Energy Function for the Simulation of Nucleic Acids, J. Am. Chem. Soc., 117, 11946-11975 (1995)

S. E. Feller, D. Yin, R. W. Pastor and A. D. MacKerell, Jr., Molecular Dynamics Simulation of Unsaturated Lipids at Low Hydration: Parametrization and Comparison with Diffraction Studies, Biophysical Journal, 73, 2269-2279 (1997) [alkenes]

R. H. Stote and M. Karplus, Zinc Binding in Proteins and Solution - A Simple but Accurate Nonbonded Representation, Proteins, 23, 12-31 (1995) [zinc ion]

Current and legacy parameter values are available from the CHARMM force field web site on Alex MacKerell's Research Interests page at the University of Maryland School of Pharmacy, https://rxsecure.umaryland.edu/research/amackere/research.html/

DUDEK.PRM

Protein-only parameters for the early 1990's TINKER force field with multipole values of Dudek and Ponder. The current file contains only the multipole values from the 1995 paper by Dudek and Ponder. This set is now superceeded by the more recent TINKER force field developed by Pengyu Ren (see WATER.PRM, below).

M. J. Dudek and J. W. Ponder, Accurate Electrostatic Modelling of the Intramolecular Energy of Proteins, J. Comput. Chem., 16, 791-816 (1995)

ENCAD.PRM

ENCAD parameters for proteins and nucleic acids. (in preparation)

M. Levitt, M. Hirshberg, R. Sharon and V. Daggett, Potential Energy Function and Parameters for Simulations of the Molecular Dynamics of Protein and Nucleic Acids in Solution, Comp. Phys. Commun., 91, 215-231 (1995)

M. Levitt, M. Hirshberg, R. Sharon, K. E. Laidig and V. Daggett, Calibration and Testing of a Water Model for Simulation of the Molecular Dynamics of Protein and Nucleic Acids in Solution, J. Phys. Chem. B, 101, 5051-5061 (1997) [F3C water]

HOCH.PRM

Simple NMR-NOE force field of Hoch and Stern.

J. C. Hoch and A. S. Stern, A Method for Determining Overall Protein Fold from NMR Distance Restraints, J. Biomol. NMR, 2, 535-543 (1992)

MM2.PRM

Full MM2(1991) parameters including p-systems. The anomeric and electronegativity correction terms included in some later versions of MM2 are not implemented.

N. L. Allinger, Conformational Analysis. 130. MM2. A Hydrocarbon Force Field Utilizing V1 and V2 Torsional Terms, J. Am. Chem. Soc., 99, 8127-8134 (1977)

J. T. Sprague, J. C. Tai, Y. Yuh and N. L. Allinger, The MMP2 Calculational Method, J. Comput. Chem., 8, 581-603 (1987)

J. C. Tai and N. L. Allinger, Molecular Mechanics Calculations on Conjugated Nitrogen-Containing Heterocycles, J. Am. Chem. Soc., 110, 2050-2055 (1988)

J. C. Tai, J.-H. Lii and N. L. Allinger, A Molecular Mechanics (MM2) Study of Furan, Thiophene, and Related Compounds, J. Comput. Chem., 10, 635-647 (1989)

N. L. Allinger, R. A. Kok and M. R. Imam, Hydrogen Bonding in MM2, J. Comput. Chem., 9, 591-595 (1988)

L. Norskov-Lauritsen and N. L. Allinger, A Molecular Mechanics Treatment of the Anomeric Effect, J. Comput. Chem., 5, 326-335 (1984)

All parameters distributed with TINKER are from the ``MM2 (1991) Parameter Set'', as provided by N. L. Allinger, University of Georgia

MM3.PRM

Full MM3(2000) parameters including pi-systems. The directional hydrogen bonding term and electronegativity bond length corrections are implemented, but the anomeric and Bohlmann correction terms are not implemented.

N. L. Allinger, Y. H. Yuh and J.-H. Lii, Molecular Mechanics. The MM3 Force Field for Hydrocarbons. 1, J. Am. Chem. Soc., 111, 8551-8566 (1989)

J.-H. Lii and N. L. Allinger, Molecular Mechanics. The MM3 Force Field for Hydrocarbons. 2. Vibrational Frequencies and Thermodynamics, J. Am. Chem. Soc., 111, 8566-8575 (1989)

J.-H. Lii and N. L. Allinger, Molecular Mechanics. The MM3 Force Field for Hydrocarbons. 3. The van der Waals' Potentials and Crystal Data for Aliphatic and Aromatic Hydrocarbons, J. Am. Chem. Soc., 111, 8576-8582 (1989)

N. L. Allinger, H. J. Geise, W. Pyckhout, L. A. Paquette and J. C. Gallucci, Structures of Norbornane and Dodecahedrane by Molecular Mechanics Calculations (MM3), X-ray Crystallography, and Electron Diffraction, J. Am. Chem. Soc., 111, 1106-1114 (1989) [stretch-torsion cross term]

N. L. Allinger, F. Li and L. Yan, Molecular Mechanics. The MM3 Force Field for Alkenes, J. Comput. Chem., 11, 848-867 (1990)

N. L. Allinger, F. Li, L. Yan and J. C. Tai, Molecular Mechanics (MM3) Calculations on Conjugated Hydrocarbons, J. Comput. Chem., 11, 868-895 (1990)

J.-H. Lii and N. L. Allinger, Directional Hydrogen Bonding in the MM3 Force Field. I, J. Phys. Org. Chem., 7, 591-609 (1994)

J.-H. Lii and N. L. Allinger, Directional Hydrogen Bonding in the MM3 Force Field. II, J. Comput. Chem., 19, 1001-1016 (1998)

All parameters distributed with TINKER are from the ``MM3 (2000) Parameter Set'', as provided by N. L. Allinger, University of Georgia, August 2000

MM3PRO.PRM

Protein-only version of the MM3 parameters.

J.-H. Lii and N. L. Allinger, The MM3 Force Field for Amides, Polypeptides and Proteins, J. Comput. Chem., 12, 186-199 (1991)

OPLSUA.PRM

Complete OPLS-UA with united-atom parameters for proteins and many classes of organic molecules. Explicit hydrogens on polar atoms and aromatic carbons.

W. L. Jorgensen and J. Tirado-Rives, The OPLS Potential Functions for Proteins. Energy Minimizations for Crystals of Cyclic Peptides and Crambin, J. Am. Chem. Soc., 110, 1657-1666 (1988) [peptide and proteins]

W. L. Jorgensen and D. L. Severance, Aromatic-Aromatic Interactions: Free Energy Profiles for the Benzene Dimer in Water, Chloroform, and Liquid Benzene, J. Am. Chem. Soc., 112, 4768-4774 (1990) [aromatic hydrogens]

S. J. Weiner, P. A. Kollman, D. A. Case, U. C. Singh, C. Ghio, G. Alagona, S. Profeta, Jr. and P. Weiner, A New Force Field for Molecular Mechanical Simulation of Nucleic Acids and Proteins, J. Am. Chem. Soc., 106, 765-784 (1984) [united-atom ``AMBER/OPLS'' local geometry]

S. J. Weiner, P. A. Kollman, D. T. Nguyen and D. A. Case, An All Atom Force Field for Simulations of Proteins and Nucleic Acids, J. Comput. Chem., 7, 230-252 (1986) [all-atom "AMBER/OPLS" local geometry]

L. X. Dang and B. M. Pettitt, Simple Intramolecular Model Potentials for Water, J. Phys. Chem., 91, 3349-3354 (1987) [flexible TIP3P and SPC water]

W. L. Jorgensen, J. D. Madura and C. J. Swenson, Optimized Intermolecular Potential Functions for Liquid Hydrocarbons, J. Am. Chem. Soc., 106, 6638-6646 (1984) [hydrocarbons]

W. L. Jorgensen, E. R. Laird, T. B. Nguyen and J. Tirado-Rives, Monte Carlo Simulations of Pure Liquid Substituted Benzenes with OPLS Potential Functions, J. Comput. Chem., 14, 206-215 (1993) [substituted benzenes]

E. M. Duffy, P. J. Kowalczyk and W. L. Jorgensen, Do Denaturants Interact with Aromatic Hydrocarbons in Water?, J. Am. Chem. Soc., 115, 9271-9275 (1993) [benzene, naphthalene, urea, guanidinium, tetramethyl ammonium]

W. L. Jorgensen and C. J. Swenson, Optimized Intermolecular Potential Functions for Amides and Peptides. Structure and Properties of Liquid Amides, J. Am. Chem. Soc., 106, 765-784 (1984) [amides]

W. L. Jorgensen, J. M. Briggs and M. L. Contreras, Relative Partition Coefficients for Organic Solutes form Fluid Simulations, J. Phys. Chem., 94, 1683-1686 (1990) [chloroform, pyridine, pyrazine, pyrimidine]

J. M. Briggs, T. B. Nguyen and W. L. Jorgensen, Monte Carlo Simulations of Liquid Acetic Acid and Methyl Acetate with the OPLS Potential Functions, J. Phys. Chem., 95, 3315-3322 (1991) [acetic acid, methyl acetate]

H. Liu, F. Muller-Plathe and W. F. van Gunsteren, A Force Field for Liquid Dimethyl Sulfoxide and Physical Properties of Liquid Dimethyl Sulfoxide Calculated Using Molecular Dynamics Simulation, J. Am. Chem. Soc., 117, 4363-4366 (1995) [dimethyl sulfoxide]

J. Gao, X. Xia and T. F. George, Importance of Bimolecular Interactions in Developing Empirical Potential Functions for Liquid Ammonia, J. Phys. Chem., 97, 9241-9246 (1993) [ammonia]

J. Aqvist, Ion-Water Interaction Potentials Derived from Free Energy Perturbation Simulations, J. Phys. Chem., 94, 8021-8024 (1990) [metal ions]

W. S. Ross and C. C. Hardin, Ion-Induced Stabilization of the G-DNA Quadruplex: Free Energy Perturbation Studies, J. Am. Chem. Soc., 116, 4363-4366 (1994) [alkali metal ions]

J. Chandrasekhar, D. C. Spellmeyer and W. L. Jorgensen, Energy Component Analysis for Dilute Aqueous Solutions of Li+, Na+, F-, and Cl- Ions, J. Am. Chem. Soc., 106, 903-910 (1984) [halide ions]

Most parameters distributed with TINKER are from ``OPLS and OPLS-AA Parameters for Organic Molecules, Ions, and Nucleic Acids'' as provided by W. L. Jorgensen, Yale University, October 1997

OPLSAA.PRM

OPLS-AA force field with all-atom parameters for proteins and many general classes of organic molecules.

W. L. Jorgensen, D. S. Maxwell and J. Tirado-Rives, Development and Testing of the OPLS All-Atom Force Field on Conformational Energetics and Properties of Organic Liquids, J. Am. Chem. Soc., 117, 11225-11236 (1996)

D. S. Maxwell, J. Tirado-Rives and W. L. Jorgensen, A Comprehensive Study of the Rotational Energy Profiles of Organic Systems by Ab Initio MO Theory, Forming a Basis for Peptide Torsional Parameters, J. Comput. Chem., 16, 984-1010 (1995)

W. L. Jorgensen and N. A. McDonald, Development of an All-Atom Force Field for Heterocycles. Properties of Liquid Pyridine and Diazenes, THEOCHEM-J. Mol. Struct., 424, 145-155 (1998)

N. A. McDonald and W. L. Jorgensen, Development of an All-Atom Force Field for Heterocycles. Properties of Liquid Pyrrole, Furan, Diazoles, and Oxazoles, J. Phys. Chem. B, 102, 8049-8059 (1998)

R. C. Rizzo and W. L. Jorgensen, OPLS All-Atom Model for Amines: Resolution of the Amine Hydration Problem, J. Am. Chem. Soc., 121, 4827-4836 (1999)

M. L. P. Price, D. Ostrovsky and W. L. Jorgensen, Gas-Phase and Liquid-State Properties of Esters, Nitriles, and Nitro Compounds with the OPLS-AA Force Field, J. Comput. Chem., 22, 1340-1352 (2001)

All parameters distributed with TINKER are from ``OPLS and OPLS-AA Parameters for Organic Molecules, Ions, and Nucleic Acids'' as provided by W. L. Jorgensen, Yale University, October 1997

OPLSAAL.PRM

An improved OPLS-AA parameter set for proteins in which the only change is a reworking of many of the backbone and sidechain torsional parameters to give better agreement with LMP2 QM calculations. This parameter set is also known as OPLS(2000).

G. A. Kaminsky, R. A. Friesner, J. Tirado-Rives and W. L. Jorgensen, Evaluation and Reparametrization of the OPLS-AA Force Field for Proteins via Comparison with Accurate Quantum Chemical Calculations on Peptides, J. Phys. Chem. B, 105, 6474-6487 (2001)

SMOOTH.PRM

Version of OPLS-UA for use with potential smoothing. Largely adapted largely from standard OPLS-UA parameters with modifications to the vdw and improper torsion terms.

R. V. Pappu, R. K. Hart and J. W. Ponder, Analysis and Application of Potential Energy Smoothing and Search Methods for Global Optimization, J. Phys, Chem. B, 102, 9725-9742 (1998) [smoothing modifications]

SMOOTHAA.PRM

Version of OPLS-AA for use with potential smoothing. Largely adapted largely from standard OPLS-AA parameters with modifications to the vdw and improper torsion terms.

WATER.PRM

The AMOEBA water parameters for a polarizable atomic multipole electrostatics model. This model is equal or better to the best available water models for many bulk and cluster properties.

P. Ren and J. W. Ponder, A Polarizable Atomic Multipole Water Model for Molecular Mechanics Simulation, J. Phys. Chem. B, 107, 5933-5947 (2003)

P. Ren and J. W. Ponder, Ion Solvation Thermodynamics from Simulation with a Polarizable Force Field, A. Grossfield, J. Am. Chem. Soc., 125, 15671-15682 (2003)

P. Ren and J. W. Ponder, Temperature and Pressure Dependence of the AMOEBA Water Model, J. Phys. Chem. B, 108, xxxx-xxxx (2004)

An earlier version the AMOEBA water model is described in: Yong Kong, Multipole Electrostatic Methods for Protein Modeling with Reaction Field Treatment, Biochemistry & Molecular Biophysics, Washington University, St. Louis, August, 1997 [available from http://dasher.wustl.edu/ponder/]

7.	Use of the Keyword Control File

This section contains a description of the keyword parameters which may be used to define or alter the course of a TINKER calculation. The keyword control file is optional in the sense that all of the TINKER programs will run in the absence of a keyfile and will simply use default values or query the user for needed information. However, the keywords allow use of a wide variety of algorithmic and procedural options, many of which are unavailable interactively.

Keywords are read from the keyword control file. All programs look first for a keyfile with the same base name as the input molecular system and ending in the extension .key. If this file does not exist, then TINKER tries to use a generic keyfile with the name tinker.key and located in the same directory as the input system. If neither a system specific nor a generic keyfile is present, TINKER will continue by using default values for keyword options and asking interactive questions as necessary.

TINKER searches the keyfile during the course of a calculation for relevant keywords that may be present. All keywords must appear as the first word on the line. Any blank space to the left of the keyword is ignored, and all contents of the keyfiles are case insensitive. Some keywords take modifiers; i.e., TINKER looks further on the same line for additional information, such as the value of some parameter related to the keyword. Modifier information is read in free format, but must be completely contained on the same line as the original keyword. Any lines contained in the keyfile which do not qualify as valid keyword lines are treated as comments and are simply ignored.

Several keywords take a list of integer values (atom numbers, for example) as modifiers. For these keywords the integers can simply be listed explicitly and separated by spaces, commas or tabs. If a range of numbers is desired, it can be specified by listing the negative of the first number of the range, followed by a separator and the last number of the range. For example, the keyword line ACTIVE 4 -9 17 23 could be used to add atoms 4, 9 through 17, and 23 to the set of active atoms during a TINKER calculation.

Listed below are the valid TINKER keywords sorted into groups by general function. The section ends with an alphabetical listing of the individual keywords along with brief descriptions of their action and possible modifiers, and examples of usage.

Keywords Grouped by Functionality

OUTPUT CONTROL KEYWORDS

ARCHIVE DEBUG DIGITS

ECHO EXIT-PAUSE NOVERSION OVERWRITE PRINTOUT SAVE-CYCLE

SAVE-FORCE SAVE-INDUCED SAVE-VELOCITY VERBOSE WRITEOUT

FORCE FIELD SELECTION KEYWORDS

FORCEFIELD PARAMETERS

POTENTIAL FUNCTION SELECTION KEYWORDS

ANGANGTERM ANGLETERM BONDTERM

CHARGETERM CHGDPLTERM DIPOLETERM

EXTRATERM IMPROPTERM IMPTORSTERM METALTERM MPOLETERM OPBENDTERM OPDISTTERM PITORSTERM POLARIZETERM

RESTRAINTERM RXNFIELDTERM SOLVATETERM STRBNDTERM STRTORTERM TORSIONTERM TORTORTERM UREYTERM VDWTERM

POTENTIAL FUNCTION PARAMETER KEYWORDS

ANGANG ANGLE ANGLE3

ANGLE4 ANGLE5 ANGLEF

ATOM BIOTYPE BOND

BOND3 BOND4 BOND5

CHARGE DIPOLE DIPOLE3

DIPOLE4 DIPOLE5 ELECTNEG

HBOND IMPROPER IMPTORS METAL MULTIPOLE OPBEND

OPDIST PIATOM PIBOND

PITORS POLARIZE SOLVATE STRBND STRTORS TORSION TORSION4 TORSION5 TORTOR

UREYBRAD VDW VDW14

VDWPR

ENERGY UNIT CONVERSION KEYWORDS

ANGLEUNIT ANGANGUNIT BONDUNIT

IMPROPUNIT IMPTORUNIT OPBENDUNIT OPDISTUNIT PITORSUNIT STRBNDUNIT

STRTORUNIT TORSIONUNIT TORTORUNIT UREYUNIT

LOCAL GEOMETRY FUNCTIONAL FORM KEYWORDS

ANGLE-CUBIC ANGLE-QUARTIC ANGLE-PENTIC

ANGLE-SEXTIC BOND-CUBIC BOND-QUARTIC BONDTYPE MM2-STRBND PISYSTEM

UREY-CUBIC UREY-QUARTIC

VAN DER WAALS FUNCTIONAL FORM KEYWORDS

A-EXPTERM B-EXPTERM C-EXPTERM

DELTA-HALGREN EPSILONRULE GAMMA-HALGREN GAUSSTYPE RADIUSRULE RADIUSSIZE RADIUSTYPE VDW-12-SCALE VDW-13-SCALE

VDW-14-SCALE VDW-15-SCALE VDWTYPE

ELECTROSTATICS FUNCTIONAL FORM KEYWORDS

CHG-12-SCALE CHG-13-SCALE CHG-14-SCALE

CHG-15-SCALE DIELECTRIC DIRECT-11-SCALE

DIRECT-12-SCALE DIRECT-13-SCALE DIRECT-14-SCALE

MPOLE-12-SCALE MPOLE-13-SCALE MPOLE-14-SCALE

MPOLE-15-SCALE MUTUAL-11-SCALE MUTUAL-12-SCALE MUTUAL-13-SCALE MUTUAL-14-SCALE POLAR-12-SCALE POLAR-13-SCALE POLAR-14-SCALE POLAR-15-SCALE POLAR-DAMP POLAR-EPS POLAR-OLD POLAR-SOR POLARIZATION REACTIONFIELD

NONBONDED CUTOFF KEYWORDS

CHG-CUTOFF CHG-TAPER CUTOFF

DPL-CUTOFF DPL-TAPER HESS-CUTOFF LIGHTS MPOLE-CUTOFF MPOLE-TAPER

NEIGHBOR-GROUPS NEUTRAL-GROUPS POLYMER-CUTOFF

TAPER TRUNCATE VDW-CUTOFF

VDW-TAPER

EWALD SUMMATION KEYWORDS

EWALD EWALD-ALPHA EWALD-BOUNDARY EWALD-CUTOFF EWALD-FRACTION PME-GRID

PME-ORDER

CRYSTAL LATTICE & PERIODIC BOUNDARY KEYWORDS

A-AXIS B-AXIS C-AXIS

ALPHA BETA GAMMA

OCTAHEDRON SPACEGROUP

OPTIMIZATION KEYWORDS

ANGMAX CAPPA FCTMIN

HGUESS INTMAX LBFGS-VECTORS MAXITER NEWHESS NEXTITER SLOPEMAX STEEPEST-DESCENT STEPMAX STEPMIN

DYNAMICS KEYWORDS

COLLISION COMPRESS DEGREES-FREEDOM

FRICTION FRICTION-SCALING INTEGRAT

TAU-PRESSURE TAU-TEMPERATURE THERMOSTAT

TRANSITION STATE KEYWORDS

DIVERGE GAMMAMIN REDUCE

SADDLEPOINT

DISTANCE GEOMETRY KEYWORDS

TRIAL-DISTANCE TRIAL-DISTRIBUTION

RANDOM NUMBER KEYWORDS

RANDOMSEED

FREE ENERGY PERTURBATION KEYWORDS

LAMBDA MUTATE

PARTIAL STRUCTURE KEYWORDS

ACTIVE GROUP GROUP-INTER

GROUP-INTRA GROUP-MOLECULE GROUP-SELECT INACTIVE

CONSTRAINT & RESTRAINT KEYWORDS

BASIN ENFORCE-CHIRALITY RATTLE

RATTLE-DISTANCE RESTRAIN-ANGLE RESTRAIN-DISTANCE RESTRAIN-GROUPS RESTRAIN-POSITION RESTRAIN-TORSION SPHERE WALL

POTENTIAL SMOOTHING KEYWORDS

DEFORM DIFFUSE-CHARGE DIFFUSE-TORSION

DIFFUSE-VDW SMOOTHING

Description of Individual Keywords

The following is an alphabetical list of the TINKER keywords along with a brief description of the action of each keyword and required or optional parameters that can be used to extend or modify each keyword. The form of possible modifiers, if any, is shown in brackets following each keyword.

A-AXIS [real] Sets the value of the a-axis length for a crystal unit cell, or, equivalently, the X-axis length for a periodic box. The length value in Angstroms is listed after the keyword.

A-EXPTERM [real] Sets the value of the ``A'' premultiplier term in the Buckingham van der Waals function, i.e., the value of A in the formula E_vdw = e { A exp[-B(R_o/R)] - C (R_o/R)⁶ }.

ACTIVE [integer list] Sets the list of active atoms during a TINKER computation. Individual potential energy terms are computed when at least one atom involved in the term is active. For Cartesian space calculations, active atoms are those allowed to move. For torsional space calculations, rotations are allowed when all atoms on one side of the rotated bond are active. Multiple ACTIVE lines can be present in the keyfile and are treated cumulatively. On each line the keyword can be followed by one or more atom numbers or atom ranges. The presence of any ACTIVE keyword overrides any INACTIVE keywords in the keyfile.

ALPHA [real] Sets the value of the a angle of a crystal unit cell, i.e., the angle between the b-axis and c-axis of a unit cell, or, equivalently, the angle between the Y-axis and Z-axis of a periodic box. The default value in the absence of the ALPHA keyword is 90 degrees.

ANGANG [1 integer & 3 reals] This keyword provides the values for a single angle-angle cross term potential parameter.

ANGANGTERM [NONE/ONLY] This keyword controls use of the angle-angle cross term potential energy. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

ANGANGUNIT [real] Sets the scale factor needed to convert the energy value computed by the angle-angle cross term potential into units of kcal/mole. The correct value is force field dependent and typically provided in the header of the master force field parameter file. The default of (p/180)² = 0.0003046 is used, if the ANGANGUNIT keyword is not given in the force field parameter file or the keyfile.

ANGLE [3 integers & 4 reals] This keyword provides the values for a single bond angle bending parameter. The integer modifiers give the atom class numbers for the three kinds of atoms involved in the angle which is to be defined. The real number modifiers give the force constant value for the angle and up to three ideal bond angles in degrees. In most cases only one ideal bond angle is given, and that value is used for all occurrences of the specified bond angle. If all three ideal angles are given, the values apply when the central atom of the angle is attached to 0, 1 or 2 additional hydrogen atoms, respectively. This ``hydrogen environment'' option is provided to implement the corresponding feature of Allinger's MM force fields. The default units for the force constant are kcal/mole/radian², but this can be controlled via the ANGLEUNIT keyword.

ANGLE-CUBIC [real] Sets the value of the cubic term in the Taylor series expansion form of the bond angle bending potential energy. The real number modifier gives the value of the coefficient as a multiple of the quadratic coefficient. This term multiplied by the angle bending energy unit conversion factor, the force constant, and the cube of the deviation of the bond angle from its ideal value gives the cubic contribution to the angle bending energy. The default value in the absence of the ANGLE-CUBIC keyword is zero; i.e., the cubic angle bending term is omitted.

ANGLE-PENTIC [real] Sets the value of the fifth power term in the Taylor series expansion form of the bond angle bending potential energy. The real number modifier gives the value of the coefficient as a multiple of the quadratic coefficient. This term multiplied by the angle bending energy unit conversion factor, the force constant, and the fifth power of the deviation of the bond angle from its ideal value gives the pentic contribution to the angle bending energy. The default value in the absence of the ANGLE-PENTIC keyword is zero; i.e., the pentic angle bending term is omitted.

ANGLE-QUARTIC [real] Sets the value of the quartic term in the Taylor series expansion form of the bond angle bending potential energy. The real number modifier gives the value of the coefficient as a multiple of the quadratic coefficient. This term multiplied by the angle bending energy unit conversion factor, the force constant, and the forth power of the deviation of the bond angle from its ideal value gives the quartic contribution to the angle bending energy. The default value in the absence of the ANGLE-QUARTIC keyword is zero; i.e., the quartic angle bending term is omitted.

ANGLE-SEXTIC [real] Sets the value of the sixth power term in the Taylor series expansion form of the bond angle bending potential energy. The real number modifier gives the value of the coefficient as a multiple of the quadratic coefficient. This term multiplied by the angle bending energy unit conversion factor, the force constant, and the sixth power of the deviation of the bond angle from its ideal value gives the sextic contribution to the angle bending energy. The default value in the absence of the ANGLE-SEXTIC keyword is zero; i.e., the sextic angle bending term is omitted.

ANGLE3 [3 integers & 4 reals] This keyword provides the values for a single bond angle bending parameter specific to atoms in 3-membered rings. The integer modifiers give the atom class numbers for the three kinds of atoms involved in the angle which is to be defined. The real number modifiers give the force constant value for the angle and up to three ideal bond angles in degrees. If all three ideal angles are given, the values apply when the central atom of the angle is attached to 0, 1 or 2 additional hydrogen atoms, respectively. The default units for the force constant are kcal/mole/radian², but this can be controlled via the ANGLEUNIT keyword. If any ANGLE3 keywords are present, either in the master force field parameter file or the keyfile, then TINKER requires that special ANGLE3 parameters be given for all angles in 3-membered rings. In the absence of any ANGLE3 keywords, standard ANGLE parameters will be used for bonds in 3-membered rings.

ANGLE4 [3 integers & 4 reals] This keyword provides the values for a single bond angle bending parameter specific to atoms in 4-membered rings. The integer modifiers give the atom class numbers for the three kinds of atoms involved in the angle which is to be defined. The real number modifiers give the force constant value for the angle and up to three ideal bond angles in degrees. If all three ideal angles are given, the values apply when the central atom of the angle is attached to 0, 1 or 2 additional hydrogen atoms, respectively. The default units for the force constant are kcal/mole/radian², but this can be controlled via the ANGLEUNIT keyword. If any ANGLE4 keywords are present, either in the master force field parameter file or the keyfile, then TINKER requires that special ANGLE4 parameters be given for all angles in 4-membered rings. In the absence of any ANGLE4 keywords, standard ANGLE parameters will be used for bonds in 4-membered rings.

ANGLE5 [3 integers & 4 reals] This keyword provides the values for a single bond angle bending parameter specific to atoms in 5-membered rings. The integer modifiers give the atom class numbers for the three kinds of atoms involved in the angle which is to be defined. The real number modifiers give the force constant value for the angle and up to three ideal bond angles in degrees. If all three ideal angles are given, the values apply when the central atom of the angle is attached to 0, 1 or 2 additional hydrogen atoms, respectively. The default units for the force constant are kcal/mole/radian², but this can be controlled via the ANGLEUNIT keyword. If any ANGLE5 keywords are present, either in the master force field parameter file or the keyfile, then TINKER requires that special ANGLE5 parameters be given for all angles in 5-membered rings. In the absence of any ANGLE5 keywords, standard ANGLE parameters will be used for bonds in 5-membered rings.

ANGLEF [3 integers & 3 reals] This keyword provides the values for a single bond angle bending parameter for a SHAPES-style Fourier potential function. The integer modifiers give the atom class numbers for the three kinds of atoms involved in the angle which is to be defined. The real number modifiers give the force constant value for the angle, the angle shift in degrees, and the periodicity value. Note that the force constant should be given as the ``harmonic'' value and not the native Fourier value. The default units for the force constant are kcal/mole/radian², but this can be controlled via the ANGLEUNIT keyword.

ANGLETERM [NONE/ONLY] This keyword controls use of the bond angle bending potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

ANGLEUNIT [real] Sets the scale factor needed to convert the energy value computed by the bond angle bending potential into units of kcal/mole. The correct value is force field dependent and typically provided in the header of the master force field parameter file. The default value of (p/180)² = 0.0003046 is used, if the ANGLEUNIT keyword is not given in the force field parameter file or the keyfile.

ANGMAX [real] Set the maximum permissible angle between the current optimization search direction and the negative of the gradient direction. If this maximum angle value is exceeded, the optimization routine will note an error condition and may restart from the steepest descent direction. The default value in the absence of the ANGMAX keyword is usually 88 degrees for conjugate gradient methods and 180 degrees (i.e., disabled) for variable metric optimizations.

ARCHIVE Causes TINKER molecular dynamics-based programs to write trajectories directly to a single plain-text archive file with the .arcformat. If an archive file already exists at the start of the calculation, then the newly generated trajectory is appended to the end of the existing file. The default in the absence of this keyword is to write the trajectory snapshots to consecutively numbered cycle files.

ATOM [2 integers, name, quoted string, integer, real & integer] This keyword provides the values needed to define a single force field atom type.

B-AXIS [real] Sets the value of the b-axis length for a crystal unit cell, or, equivalently, the Y-axis length for a periodic box. The length value in Angstroms is listed after the keyword. If the keyword is absent, the b-axis length is set equal to the a-axis length.

B-EXPTERM [real] Sets the value of the ``B'' exponential factor in the Buckingham van der Waals function, i.e., the value of B in the formula E_vdw = e { A exp[-B(R_o/R)] - C (R_o/R)⁶ }.

BASIN [2 reals] Presence of this keyword turns on a ``basin'' restraint potential function that serves to drive the system toward a compact structure. The actual function is a Gaussian of the form E_basin = S A exp[-B R²], summed over all pairs of atoms where R is the distance between atoms. The A and B values are the depth and width parameters given as modifiers to the BASIN keyword. This potential is currently used to control the degree of expansion during potential energy smooth procedures through the use of shallow, broad basins.

BETA [real] Sets the value of the b angle of a crystal unit cell, i.e., the angle between the a-axis and c-axis of a unit cell, or, equivalently, the angle between the X-axis and Z-axis of a periodic box. The default value in the absence of the BETA keyword is to set the b angle equal to the a angle as given by the keyword ALPHA.

BIOTYPE [integer, name, quoted string & integer] This keyword provides the values to define the correspondence between a single biopolymer atom type and its force field atom type.

BOND [2 integers & 2 reals] This keyword provides the values for a single bond stretching parameter. The integer modifiers give the atom class numbers for the two kinds of atoms involved in the bond which is to be defined. The real number modifiers give the force constant value for the bond and the ideal bond length in Å. The default units for the force constant are kcal/mole/Å², but this can be controlled via the BONDUNIT keyword.

BOND-CUBIC [real] Sets the value of the cubic term in the Taylor series expansion form of the bond stretching potential energy. The real number modifier gives the value of the coefficient as a multiple of the quadratic coefficient. This term multiplied by the bond stretching energy unit conversion factor, the force constant, and the cube of the deviation of the bond length from its ideal value gives the cubic contribution to the bond stretching energy. The default value in the absence of the BOND-CUBIC keyword is zero; i.e., the cubic bond stretching term is omitted.

BOND-QUARTIC [real] Sets the value of the quartic term in the Taylor series expansion form of the bond stretching potential energy. The real number modifier gives the value of the coefficient as a multiple of the quadratic coefficient. This term multiplied by the bond stretching energy unit conversion factor, the force constant, and the forth power of the deviation of the bond length from its ideal value gives the quartic contribution to the bond stretching energy. The default value in the absence of the BOND-QUARTIC keyword is zero; i.e., the quartic bond stretching term is omitted.

BOND3 [2 integers & 2 reals] This keyword provides the values for a single bond stretching parameter specific to atoms in 3-membered rings. The integer modifiers give the atom class numbers for the two kinds of atoms involved in the bond which is to be defined. The real number modifiers give the force constant value for the bond and the ideal bond length in Å. The default units for the force constant are kcal/mole/Å², but this can be controlled via the BONDUNIT keyword. If any BOND3 keywords are present, either in the master force field parameter file or the keyfile, then TINKER requires that special BOND3 parameters be given for all bonds in 3-membered rings. In the absence of any BOND3 keywords, standard BOND parameters will be used for bonds in 3-membered rings.

BOND4 [2 integers & 2 reals] This keyword provides the values for a single bond stretching parameter specific to atoms in 4-membered rings. The integer modifiers give the atom class numbers for the two kinds of atoms involved in the bond which is to be defined. The real number modifiers give the force constant value for the bond and the ideal bond length in Å. The default units for the force constant are kcal/mole/Å², but this can be controlled via the BONDUNIT keyword. If any BOND4 keywords are present, either in the master force field parameter file or the keyfile, then TINKER requires that special BOND4 parameters be given for all bonds in 4-membered rings. In the absence of any BOND4 keywords, standard BOND parameters will be used for bonds in 4-membered rings

BOND5 [2 integers & 2 reals] This keyword provides the values for a single bond stretching parameter specific to atoms in 5-membered rings. The integer modifiers give the atom class numbers for the two kinds of atoms involved in the bond which is to be defined. The real number modifiers give the force constant value for the bond and the ideal bond length in Å. The default units for the force constant are kcal/mole/Å², but this can be controlled via the BONDUNIT keyword. If any BOND5 keywords are present, either in the master force field parameter file or the keyfile, then TINKER requires that special BOND5 parameters be given for all bonds in 5-membered rings. In the absence of any BOND5 keywords, standard BOND parameters will be used for bonds in 5-membered rings

BONDTERM [NONE/ONLY] This keyword controls use of the bond stretching potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

BONDTYPE [TAYLOR/MORSE/GAUSSIAN] Chooses the functional form of the bond stretching potential. The TAYLOR option selects a Taylor series expansion containing terms from harmonic through quartic. The MORSE option selects a Morse potential fit to the ideal bond length and stretching force constant parameter values. The GAUSSIAN option uses an inverted Gaussian with amplitude equal to the Morse bond dissociation energy and width set to reproduce the vibrational frequency of a harmonic potential. The default is to use the TAYLOR potential.

BONDUNIT [real] Sets the scale factor needed to convert the energy value computed by the bond stretching potential into units of kcal/mole. The correct value is force field dependent and typically provided in the header of the master force field parameter file. The default value of 1.0 is used, if the BONDUNIT keyword is not given in the force field parameter file or the keyfile.

C-AXIS [real] Sets the value of the C-axis length for a crystal unit cell, or, equivalently, the Z-axis length for a periodic box. The length value in Angstroms is listed after the keyword. If the keyword is absent, the C-axis length is set equal to the A-axis length.

C-EXPTERM [real] Sets the value of the ``C'' dispersion multiplier in the Buckingham van der Waals function, i.e., the value of C in the formula E_vdw = e { A exp[-B(R_o/R)] - C (R_o/R)⁶ }.

CAPPA [real] This keyword is used to set the normal termination criterion for the line search phase of TINKER optimization routines. The line search exits successfully if the ratio of the current gradient projection on the line to the projection at the start of the line search falls below the value of CAPPA. A default value of 0.1 is used in the absence of the CAPPA keyword.

CHARGE [1 integer & 1 real] This keyword provides a value for a single atomic partial charge electrostatic parameter. The integer modifier, if positive, gives the atom type number for which the charge parameter is to be defined. Note that charge parameters are given for atom types, not atom classes. If the integer modifier is negative, then the parameter value to follow applies only to the individual atom whose atom number is the negative of the modifier. The real number modifier gives the values of the atomic partial charge in electrons.

CHARGETERM [NONE/ONLY] This keyword controls use of the charge-charge potential energy term between pairs of atomic partial charges. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

CHG-12-SCALE [real] This keyword provides a multiplicative scale factor that is applied to charge-charge electrostatic interactions between 1-2 connected atoms, i.e., atoms that are directly bonded. The default value of 0.0 is used, if the CHG-12-SCALE keyword is not given in either the parameter file or the keyfile.

CHG-13-SCALE [real] This keyword provides a multiplicative scale factor that is applied to charge-charge electrostatic interactions between 1-3 connected atoms, i.e., atoms separated by two covalent bonds. The default value of 0.0 is used, if the CHG-13-SCALE keyword is not given in either the parameter file or the keyfile.

CHG-14-SCALE [real] This keyword provides a multiplicative scale factor that is applied to charge-charge electrostatic interactions between 1-4 connected atoms, i.e., atoms separated by three covalent bonds. The default value of 1.0 is used, if the CHG-14-SCALE keyword is not given in either the parameter file or the keyfile.

CHG-15-SCALE [real] This keyword provides a multiplicative scale factor that is applied to charge-charge electrostatic interactions between 1-5 connected atoms, i.e., atoms separated by four covalent bonds. The default value of 1.0 is used, if the CHG-15-SCALE keyword is not given in either the parameter file or the keyfile.

CHG-CUTOFF [real] Sets the cutoff distance value in Angstroms for charge-charge electrostatic potential energy interactions. The energy for any pair of sites beyond the cutoff distance will be set to zero. Other keywords can be used to select a smoothing scheme near the cutoff distance. The default cutoff distance in the absence of the CHG-CUTOFF keyword is infinite for nonperiodic systems and 9.0 for periodic systems.

CHG-TAPER [real] This keyword allows modification of the cutoff window for charge-charge electrostatic potential energy interactions. It is similar in form and action to the TAPER keyword, except that its value applies only to the charge-charge potential. The default value in the absence of the CHG-TAPER keyword is to begin the cutoff window at 0.65 of the corresponding cutoff distance.

CHGDPLTERM [NONE/ONLY] This keyword controls use of the charge-dipole potential energy term between atomic partial charges and bond dipoles. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

COLLISION [real] Sets the value of the random collision frequency used in the Andersen stochastic collision dynamics thermostat. The supplied value has units of fs^-1 atom^-1 and is multiplied internal to TINKER by the time step in fs and N^-2/3 where N is the number of atoms. The default value used in the absence of the COLLISION keyword is 0.1 which is appropriate for many systems but may need adjustment to achieve adequate temperature control without perturbing the dynamics.

COMPRESS [real] Sets the value of the bulk solvent isothermal compressibility in Atm^-1 for use during pressure computation and scaling in molecular dynamics computations. The default value used in the absence of the COMPRESS keyword is 0.000046, appropriate for water. This parameter serves as a scale factor for the Groningen-style pressure bath coupling time, and its exact value should not be of critical importance.

CUTOFF [real] Sets the cutoff distance value for all nonbonded potential energy interactions. The energy for any of the nonbonded potentials of a pair of sites beyond the cutoff distance will be set to zero. Other keywords can be used to select a smoothing scheme near the cutoff distance, or to apply different cutoff distances to various nonbonded energy terms.

DEBUG Turns on printing of detailed information and intermediate values throughout the progress of a TINKER computation; not recommended for use with large structures or full potential energy functions since a summary of every individual interaction will usually be output.

DEFORM [real] Sets the amount of diffusion equation-style smoothing that will be applied to the potential energy surface when using the SMOOTH force field. The real number option is equivalent to the ``time'' value in the original Piela, et al. formalism; the larger the value, the greater the smoothing. The default value is zero, meaning that no smoothing will be applied.

DEGREES-FREEDOM [integer] This keyword allows manual setting of the number of degrees of freedom during a dynamics calculation. The integer modifier is used by thermostating methods and in other places as the number of degrees of freedom, overriding the value determined by the TINKER code at dynamics startup. In the absence of the keyword, the programs will automatically compute the correct value based on the number of atoms active during dynamics, bond or other constrains, and use of periodic boundary conditions.

DELTA-HALGREN [real] Sets the value of the d parameter in Halgren's buffered 14-7 vdw potential energy functional form. In the absence of the DELTA-HALGREN keyword, a default value of 0.07 is used.

DIELECTRIC [real] Sets the value of the bulk dielectric constant used to damp all electrostatic interaction energies for any of the TINKER electrostatic potential functions. The default value is force field dependent, but is usually equal to 1.0 (for Allinger's MM force fields the default is 1.5).

DIFFUSE-CHARGE [real] This keyword is used during potential function smoothing procedures to specify the effective diffusion coefficient to be applied to the smoothed form of the Coulomb's Law charge-charge potential function. In the absence of the DIFFUSE-CHARGE keyword, a default value of 3.5 is used.

DIFFUSE-TORSION [real] This keyword is used during potential function smoothing procedures to specify the effective diffusion coefficient to be applied to the smoothed form of the torsion angle potential function. In the absence of the DIFFUSE-TORSION keyword, a default value of 0.0225 is used.

DIFFUSE-VDW [real] This keyword is used during potential function smoothing procedures to specify the effective diffusion coefficient to be applied to the smoothed Gaussian approximation to the Lennard-Jones van der Waals potential function. In the absence of the DIFFUSE-VDW keyword, a default value of 1.0 is used.

DIGITS [integer] This keyword controls the number of digits of precision output by TINKER in reporting potential energies and atomic coordinates. The allowed values for the integer modifier are 4, 6 and 8. Input values less than 4 will be set to 4, and those greater than 8 will be set to 8. Final energy values reported by most TINKER programs will contain the specified number of digits to the right of the decimal point. The number of decimal places to be output for atomic coordinates is generally two larger than the value of DIGITS. In the absence of the DIGITS keyword a default value of 4 is used, and energies will be reported to 4 decimal places with coordinates to 6 decimal places.

DIPOLE [2 integers & 2 reals] This keyword provides the values for a single bond dipole electrostatic parameter. The integer modifiers give the atom type numbers for the two kinds of atoms involved in the bond dipole which is to be defined. The real number modifiers give the value of the bond dipole in Debyes and the position of the dipole site along the bond. If the bond dipole value is positive, then the first of the two atom types is the positive end of the dipole. For a negative bond dipole value, the first atom type listed is negative. The position along the bond is an optional modifier that gives the postion of the dipole site as a fraction between the first atom type (position=0) and the second atom type (position=1). The default for the dipole position in the absence of a specified value is 0.5, placing the dipole at the midpoint of the bond.

DIPOLE3 [2 integers & 2 reals] This keyword provides the values for a single bond dipole electrostatic parameter specific to atoms in 3-membered rings. The integer modifiers give the atom type numbers for the two kinds of atoms involved in the bond dipole which is to be defined. The real number modifiers give the value of the bond dipole in Debyes and the position of the dipole site along the bond. The default for the dipole position in the absence of a specified value is 0.5, placing the dipole at the midpoint of the bond. If any DIPOLE3 keywords are present, either in the master force field parameter file or the keyfile, then TINKER requires that special DIPOLE3 parameters be given for all bond dipoles in 3-membered rings. In the absence of any DIPOLE3 keywords, standard DIPOLE parameters will be used for bonds in 3-membered rings.

DIPOLE4 [2 integers & 2 reals] This keyword provides the values for a single bond dipole electrostatic parameter specific to atoms in 4-membered rings. The integer modifiers give the atom type numbers for the two kinds of atoms involved in the bond dipole which is to be defined. The real number modifiers give the value of the bond dipole in Debyes and the position of the dipole site along the bond. The default for the dipole position in the absence of a specified value is 0.5, placing the dipole at the midpoint of the bond. If any DIPOLE4 keywords are present, either in the master force field parameter file or the keyfile, then TINKER requires that special DIPOLE4 parameters be given for all bond dipoles in 4-membered rings. In the absence of any DIPOLE4 keywords, standard DIPOLE parameters will be used for bonds in 4-membered rings.

DIPOLE5 [2 integers & 2 reals] This keyword provides the values for a single bond dipole electrostatic parameter specific to atoms in 5-membered rings. The integer modifiers give the atom type numbers for the two kinds of atoms involved in the bond dipole which is to be defined. The real number modifiers give the value of the bond dipole in Debyes and the position of the dipole site along the bond. The default for the dipole position in the absence of a specified value is 0.5, placing the dipole at the midpoint of the bond. If any DIPOLE5 keywords are present, either in the master force field parameter file or the keyfile, then TINKER requires that special DIPOLE5 parameters be given for all bond dipoles in 5-membered rings. In the absence of any DIPOLE5 keywords, standard DIPOLE parameters will be used for bonds in 5-membered rings.

DIPOLETERM [NONE/ONLY] This keyword controls use of the dipole-dipole potential energy term between pairs of bond dipoles. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

DIRECT-11-SCALE [real] This keyword provides a multiplicative scale factor that is applied to the permanent (direct) field due to atoms within a polarization group during an induced dipole calculation, i.e., atoms that are in the same polarization group as the atom being polarized. The default value of 0.0 is used, if the DIRECT-11-SCALE keyword is not given in either the parameter file or the keyfile.

DIRECT-12-SCALE [real] This keyword provides a multiplicative scale factor that is applied to the permanent (direct) field due to atoms in 1-2 polarization groups during an induced dipole calculation, i.e., atoms that are in polarization groups directly connected to the group containing the atom being polarized. The default value of 0.0 is used, if the DIRECT-12-SCALE keyword is not given in either the parameter file or the keyfile.

DIRECT-13-SCALE [real] This keyword provides a multiplicative scale factor that is applied to the permanent (direct) field due to atoms in 1-3 polarization groups during an induced dipole calculation, i.e., atoms that are in polarization groups separated by one group from the group containing the atom being polarized. The default value of 0.0 is used, if the DIRECT-13-SCALE keyword is not given in either the parameter file or the keyfile.

DIRECT-14-SCALE [real] This keyword provides a multiplicative scale factor that is applied to the permanent (direct) field due to atoms in 1-4 polarization groups during an induced dipole calculation, i.e., atoms that are in polarization groups separated by two groups from the group containing the atom being polarized. The default value of 1.0 is used, if the DIRECT-14-SCALE keyword is not given in either the parameter file or the keyfile.

DIVERGE [real] This keyword is used by the SADDLE program to set the maximum allowed value of the ratio of the gradient length along the path to the total gradient norm at the end of a cycle of minimization perpendicular to the path. If the value provided by the DIVERGE keyword is exceeded, then another cycle of maximization along the path is required. A default value of 0.005 is used in the absence of the DIVERGE keyword.

DPL-CUTOFF [real] Sets the cutoff distance value in Angstroms for bond dipole-bond dipole electrostatic potential energy interactions. The energy for any pair of bond dipole sites beyond the cutoff distance will be set to zero. Other keywords can be used to select a smoothing scheme near the cutoff distance. The default cutoff distance in the absence of the DPL-CUTOFF keyword is essentially infinite for nonperiodic systems and 10.0 for periodic systems.

DPL-TAPER [real] This keyword allows modification of the cutoff windows for bond dipole-bond dipole electrostatic potential energy interactions. It is similar in form and action to the TAPER keyword, except that its value applies only to the vdw potential. The default value in the absence of the DPL-TAPER keyword is to begin the cutoff window at 0.75 of the dipole cutoff distance.

ECHO [text string] The presence of this keyword causes whatever text follows it on the line to be copied directly to the output file. This keyword is also active in parameter files. It has no default value; if no text follows the ECHO keyword, a blank line is placed in the output file.

ELECTNEG [3 integers & 1 real] This keyword provides the values for a single electronegativity bond length correction parameter. The first two integer modifiers give the atom class numbers of the atoms involved in the bond to be corrected. The third integer modifier is the atom class of an electronegative atom. In the case of a primary correction, an atom of this third class must be directly bonded to an atom of the second atom class. For a secondary correction, the third class is one atom removed from an atom of the second class. The real number modifier is the value in Å by which the original ideal bond length is to be corrected.

ENFORCE-CHIRALITY This keyword causes the chirality found at chiral tetravalent centers in the input structure to be maintained during TINKER calculations. The test for chirality is not exhaustive; two identical monovalent atoms connected to a center cause it to be marked as non-chiral, but large equivalent substituents are not detected. Trivalent ``chiral'' centers, for example the alpha carbon in united-atom protein structures, are not enforced as chiral.

EPSILONRULE [GEOMETRIC/ARITHMETIC/HARMONIC/HHG] This keyword selects the combining rule used to derive the e value for van der Waals interactions. The default in the absence of the EPSILONRULE keyword is to use the GEOMETRIC mean of the individual e values of the two atoms involved in the van der Waals interaction.

EWALD This keyword turns on the use of Ewald summation during computation of electrostatic interactions in periodic systems. In the current version of TINKER, regular Ewald is used for polarizable atomic multipoles, and smooth particle mesh Ewald (PME) is used for charge-charge interactions. Ewald summation is not available for interactions involving bond-centered dipoles. By default, in the absence of the EWALD keyword, distance-based cutoffs are used for electrostatic interactions.

EWALD-ALPHA [real] Sets the value of the Ewald coefficient which controls the width of the Gaussian screening charges during particle mesh Ewald summation. In the absence of the EWALD-ALPHA keyword, a value is chosen which causes interactions outside the real-space cutoff to be below a fixed tolerance. For most standard applications of Ewald summation, the program default should be used.

EWALD-BOUNDARY This keyword invokes the use of ``vacuum'' boundary conditions during Ewald summation, corresponding to the media surrounding the system having a dielectric value of 1. The default in the absence of the EWALD-BOUNDARY keyword is to use ``tinfoil'' boundary conditions where the surrounding media is assumed to have an infinite dielectric value.

EWALD-CUTOFF [real] Sets the value in Angstroms of the real-space distance cutoff for use during Ewald summation. By default, in the absence of the EWALD-CUTOFF keyword, a value of 9.0 is used.

EWALD-FRACTION [real] Sets the fraction between 0 and 1 of reciprocal space included in the reciprocal sum when using regular Ewald summation. The keyword has no effect on PME calculations. A default value of 0.5 is used in the absence of the EWALD-FRACTION keyword.

EXIT-PAUSE This keyword causes TINKER programs to pause and wait for a carriage return at the end of executation prior to returning control to the operating system. This is useful to keep the execution window open following termination on machines running Microsoft Windows or Apple MacOS. The default in the absence of the EXIT-PAUSE keyword, is to return control to the operating system immediately at program termination.

EXTRATERM [NONE/ONLY] This keyword controls use of the user defined extra potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

FCTMIN [real] This keyword sets a convergence criterion for successful completion of a TINKER optimization. If the value of the optimization objective function, typically the potential energy, falls below the value set by FCTMIN, then the optimization is deemed to have converged. The default value in the absence of the FCTMIN keyword is -1000000, effectively removing this criterion as a possible agent for termination.

FORCEFIELD [name] This keyword provides a name for the force field to be used in the current calculation. Its value is usually set in the master force field parameter file for the calculation (see the PARAMETERS keyword) instead of in the keyfile.

FRICTION [real] Sets the value of the frictional coefficient in ps^-1 for use with stochastic dynamics. The default value used in the absence of the FRICTION keyword is 91.0, which is generally appropriate for water.

GAMMA [real] Sets the value of the g angle of a crystal unit cell, i.e., the angle between the a-axis and b-axis of a unit cell, or, equivalently, the angle between the X-axis and Z-axis of a periodic box. The default value in the absence of the GAMMA keyword is to set the g angle equal to the a angle as given by the keyword ALPHA.

GAMMA-HALGREN [real] Sets the value of the g parameter in Halgren's buffered 14-7 vdw potential energy functional form. In the absence of the DELTA-HALGREN keyword, a default value of 0.12 is used.

GAMMAMIN [real] Sets the convergence target value for g during searches for maxima along the quadratic synchronous transit used by the SADDLE program. The value of g is the square of the ratio of the gradient projection along the path to the total gradient. A default value of 0.00001 is used in the absence of the GAMMAMIN keyword.

GAUSSTYPE [LJ-2/LJ-4/MM2-2/MM3-2/IN-PLACE] This keyword specifies the underlying vdw form that a Gaussian vdw approximation will attempt to fit.number of terms to be used in a Gaussian approximation of the Lennard-Jones van der Waals potential. The text modifier gives the name of the functional form to be used. Thus LJ-2 as a modifier will result in a 2-Gaussian fit to a Lennard-Jones vdw potential. The GAUSSTYPE keyword only takes effect when VDWTYPE is set to GAUSSIAN. This keyword has no default value.

GROUP [integer, integer list] This keyword defines an atom group as a substructure within the full input molecular structure. The value of the first integer is the group number which must be in the range from 1 to the maximum number of allowed groups. The remaining intergers give the atom or atoms contained in this group as one or more atom numbers or ranges. Multiple keyword lines can be used to specify additional atoms in the same group. Note that an atom can only be in one group, the last group to which it is assigned is the one used.

GROUP-INTER This keyword assigns a value of 1.0 to all inter-group interactions and a value of 0.0 to all intra-group interactions. For example, combination with the GROUP-MOLECULE keyword provides for rigid-body calculations.

GROUP-INTRA This keyword assigns a value of 1.0 to all intra-group interactions and a value of 0.0 to all inter-group interactions.

GROUP-MOLECULE This keyword sets each individual molecule in the system to be a separate atom group, but does not assign weights to group-group interactions.

GROUP-SELECT [2 integers, real] This keyword gives the weight in the final potential energy of a specified set of intra- or intergroup interactions. The integer modifiers give the group numbers of the groups involved. If the two numbers are the same, then an intragroup set of interactions is specified. The real modifier gives the weight by which all energetic interactions in this set will be multiplied before incorporation into the final potential energy. If omitted as a keyword modifier, the weight will be set to 1.0 by default. If any SELECT-GROUP keywords are present, then any set of interactions not specified in a SELECT-GROUP keyword is given a zero weight. The default when no SELECT-GROUP keywords are specified is to use all intergroup interactions with a weight of 1.0 and to set all intragroup interactions to zero.

HBOND [2 integers & 2 reals] This keyword provides the values for the MM3-style directional hydrogen bonding parameters for a single pair of atoms. The integer modifiers give the pair of atom class numbers for which hydrogen bonding parameters are to be defined. The two real number modifiers give the values of the minimum energy contact distance in Å and the well depth at the minimum distance in kcal/mole.

HESS-CUTOFF [real] This keyword defines a lower limit for significant Hessian matrix elements. During computation of the Hessian matrix of partial second derivatives, any matrix elements with absolute value below HESS-CUTOFF will be set to zero and omitted from the sparse matrix Hessian storage scheme used by TINKER. For most calculations, the default in the absence of this keyword is zero, i.e., all elements will be stored. For most Truncated Newton optimizations the Hessian cutoff will be chosen dynamically by the optimizer.

HGUESS [real] Sets an initial guess for the average value of the diagonal elements of the scaled inverse Hessian matrix used by the optimally conditioned variable metric optimization routine. A default value of 0.4 is used in the absence of the HGUESS keyword.

IMPROPER [4 integers & 2 reals] This keyword provides the values for a single CHARMM-style improper dihedral angle parameter.

IMPROPTERM [NONE/ONLY] This keyword controls use of the CHARMM-style improper dihedral angle potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

IMPROPUNIT [real] Sets the scale factor needed to convert the energy value computed by the CHARMM-style improper dihedral angle potential into units of kcal/mole. The correct value is force field dependent and typically provided in the header of the master force field parameter file. The default value of 1.0 is used, if the IMPROPUNIT keyword is not given in the force field parameter file or the keyfile.

IMPTORS [4 integers & up to 3 real/real/integer triples] This keyword provides the values for a single AMBER-style improper torsional angle parameter. The first four integer modifiers give the atom class numbers for the atoms involved in the improper torsional angle to be defined. By convention, the third atom class of the four is the trigonal atom on which the improper torsion is centered. The torsional angle computed is literally that defined by the four atom classes in the order specified by the keyword. Each of the remaining triples of real/real/integer modifiers give the half-amplitude, phase offset in degrees and periodicity of a particular improper torsional term, respectively. Periodicities through 3-fold are allowed for improper torsional parameters.

IMPTORSTERM [NONE/ONLY] This keyword controls use of the AMBER-style improper torsional angle potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

IMPTORSUNIT [real] Sets the scale factor needed to convert the energy value computed by the AMBER-style improper torsional angle potential into units of kcal/mole. The correct value is force field dependent and typically provided in the header of the master force field parameter file. The default value of 1.0 is used, if the IMPTORSUNIT keyword is not given in the force field parameter file or the keyfile.

INACTIVE [integer list] Sets the list of inactive atoms during a TINKER computation. Individual potential energy terms are not computed when all atoms involved in the term are inactive. For Cartesian space calculations, inactive atoms are not allowed to move. For torsional space calculations, rotations are not allowed when there are inactive atoms on both sides of the rotated bond. Multiple INACTIVE lines can be present in the keyfile, and on each line the keyword can be followed by one or more atom numbers or ranges. If any INACTIVE keys are found, all atoms are set to active except those listed on the INACTIVE lines. The ACTIVE keyword overrides all INACTIVE keywords found in the keyfile.

INTEGRATE [VERLET/BEEMAN/STOCHASTIC/RIGIDBODY] Chooses the integration method for propagation of dynamics trajectories. The keyword is followed on the same line by the name of the option. Standard Newtonian MD can be run using either VERLET for the Velocity Verlet method, or BEEMAN for the velocity form of Bernie Brook's ``Better Beeman'' method. A Velocity Verlet-based stochastic dynamics trajectory is selected by the STOCHASTIC modifier. A rigid-body dynamics method is selected by the RIGIDBODY modifier. The default integration scheme is MD using the BEEMAN method.

INTMAX [integer] Sets the maximum number of interpolation cycles that will be allowed during the line search phase of an optimization. All gradient-based TINKER optimization routines use a common line search routine involving quadratic extrapolation and cubic interpolation. If the value of INTMAX is reached, an error status is set for the line search and the search is repeated with a much smaller initial step size. The default value in the absence of this keyword is optimization routine dependent, but is usually in the range 5 to 10.

LAMBDA [real] This keyword sets the value of the l path parameter for free energy perturbation calculations. The real number modifier specifies the position along the mutation path and must be a number in the range from 0 (initial state) to 1 (final state). The actual atoms involved in the mutation are given separately in individual MUTATE keyword lines.

LBFGS-VECTORS [integer] Sets the number of correction vectors used by the limited-memory L-BFGS optimization routine. The current maximum allowable value, and the default in the absence of the LBFGS-VECTORS keyword is 15.

LIGHTS This keyword turns on Method of Lights neighbor generation for the charge-charge potential and any of the van der Waals potentials. This method will yield identical energetic results to the standard double loop method. Method of Lights will be faster when the volume of a sphere with radius equal to the nonbond cutoff distance is significantly less than half the volume of the total system (i.e., the full molecular system, the crystal unit cell or the periodic box).

MAXITER [integer] Sets the maximum number of minimization iterations that will be allowed for any TINKER program that uses any of the nonlinear optimization routines. The default value in the absence of this keyword is program dependent, but is always set to a very large number.

METAL This keyword provides the values for a single transition metal ligand field parameter. Note this keyword is present in the code, but not active in the current version of TINKER.

METALTERM [NONE/ONLY] This keyword controls use of the transition metal ligand field potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

MM2-STRBND This keyword switches the behavior of the stretch-bend potential function to match the formulation used by the MM2 force field. In MM2, stretching of bonds to attached hydrogen atoms is not including in computing the stretch-bend cross term energy. The default behavior in the absence of this keyword is to include stretching of attached hydrogen atoms as in the MM3 force field.

MPOLE-12-SCALE [real] This keyword provides a multiplicative scale factor that is applied to permanent atomic multipole electrostatic interactions between 1-2 connected atoms, i.e., atoms that are directly bonded. The default value of 0.0 is used, if the MPOLE-12-SCALE keyword is not given in either the parameter file or the keyfile.

MPOLE-13-SCALE [real] This keyword provides a multiplicative scale factor that is applied to permanent atomic multipole electrostatic interactions between 1-3 connected atoms, i.e., atoms separated by two covalent bonds. The default value of 0.0 is used, if the MPOLE-13-SCALE keyword is not given in either the parameter file or the keyfile.

MPOLE-14-SCALE [real] This keyword provides a multiplicative scale factor that is applied to permanent atomic multipole electrostatic interactions between 1-4 connected atoms, i.e., atoms separated by three covalent bonds. The default value of 1.0 is used, if the MPOLE-14-SCALE keyword is not given in either the parameter file or the keyfile.

MPOLE-15-SCALE [real] This keyword provides a multiplicative scale factor that is applied to permanent atomic multipole electrostatic interactions between 1-5 connected atoms, i.e., atoms separated by four covalent bonds. The default value of 1.0 is used, if the MPOLE-15-SCALE keyword is not given in either the parameter file or the keyfile.

MPOLE-CUTOFF [real] Sets the cutoff distance value in Angstroms for atomic multipole potential energy interactions. The energy for any pair of sites beyond the cutoff distance will be set to zero. Other keywords can be used to select a smoothing scheme near the cutoff distance. The default cutoff distance in the absence of the MPOLE-CUTOFF keyword is infinite for nonperiodic systems and 9.0 for periodic systems.

MPOLE-TAPER [real] This keyword allows modification of the cutoff window for atomic multipole potential energy interactions. It is similar in form and action to the TAPER keyword, except that its value applies only to the atomic multipole potential. The default value in the absence of the MPOLE-TAPER keyword is to begin the cutoff window at 0.65 of the corresponding cutoff distance.

MPOLETERM [NONE/ONLY] This keyword controls use of the atomic multipole electrostatics potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

MULTIPOLE [5 lines with: 3 or 4 integers & 1 real; 3 reals; 1 real; 2 reals; 3 reals] This keyword provides the values for a set of atomic multipole parameters at a single site. A complete keyword entry consists of three consequtive lines, the first line containing the MULTIPOLE keyword and the two following lines. The first line contains three integers which define the atom type on which the multipoles are centered, and the Z-axis and X-axis defining atom types for this center. The optional fourth integer contains the Y-axis defining atom type, and is only required for locally chiral multipole sites. The real number on the first line gives the monopole (atomic charge) in electrons. The second line contains three real numbers which give the X-, Y- and Z-components of the atomic dipole in electron-Å. The final three lines, consisting of one, two and three real numbers give the upper triangle of the traceless atomic quadrupole tensor in electron-Å².

MUTATE [3 integers] This keyword is used to specify atoms to be mutated during free energy perturbation calculations. The first integer modifier gives the atom number of an atom in the current system. The final two modifier values give the atom types corresponding the the l=0 and l=1 states of the specified atom.

MUTUAL-11-SCALE [real] This keyword provides a multiplicative scale factor that is applied to the induced (mutual) field due to atoms within a polarization group during an induced dipole calculation, i.e., atoms that are in the same polarization group as the atom being polarized. The default value of 1.0 is used, if the MUTUAL-11-SCALE keyword is not given in either the parameter file or the keyfile.

MUTUAL-12-SCALE [real] This keyword provides a multiplicative scale factor that is applied to the induced (mutual) field due to atoms in 1-2 polarization groups during an induced dipole calculation, i.e., atoms that are in polarization groups directly connected to the group containing the atom being polarized. The default value of 1.0 is used, if the MUTUAL-12-SCALE keyword is not given in either the parameter file or the keyfile.

MUTUAL-13-SCALE [real] This keyword provides a multiplicative scale factor that is applied to the induced (mutual) field due to atoms in 1-3 polarization groups during an induced dipole calculation, i.e., atoms that are in polarization groups separated by one group from the group containing the atom being polarized. The default value of 1.0 is used, if the MUTUAL-13-SCALE keyword is not given in either the parameter file or the keyfile.

MUTUAL-14-SCALE [real] This keyword provides a multiplicative scale factor that is applied to the induced (mutual) field due to atoms in 1-4 polarization groups during an induced dipole calculation, i.e., atoms that are in polarization groups separated by two groups from the group containing the atom being polarized. The default value of 1.0 is used, if the MUTUAL-14-SCALE keyword is not given in either the parameter file or the keyfile.

NEIGHBOR-GROUPS This keyword causes the attached atom to be used in determining the charge-charge neighbor distance for all monovalent atoms in the molecular system. Its use causes all monovalent atoms to be treated the same as their attached atoms for purposes of including or scaling 1-2, 1-3 and 1-4 interactions. This option works only for the simple charge-charge electrostatic potential; it does not affect bond dipole or atomic multipole potentials. The NEIGHBOR-GROUPS scheme is similar to that used by some common force fields such as ENCAD.

NEUTRAL-GROUPS The keyword causes the attached atom to be used in determining the charge-charge interaction cutoff distance for all monovalent atoms in the molecular system. Its use reduces cutoff discontinuities by avoiding splitting many of the largest charge separations found in typical molecules. Note that this keyword does not rigorously implement the usual concept of a ``neutral group'' as used in the literature with AMBER/OPLS and other force fields. This option works only for the simple charge-charge electrostatic potential; it does not affect bond dipole or atomic multipole potentials.

NEWHESS [integer] Sets the number of algorithmic iterations between recomputation of the Hessian matrix. At present this keyword applies exclusively to optimizations using the Truncated Newton method. The default value in the absence of this keyword is 1, i.e., the Hessian is computed on every iteration.

NEXTITER [integer] Sets the iteration number to be used for the first iteration of the current computation. At present this keyword applies to optimization procedures where its use can effect convergence criteria, timing of restarts, and so forth. The default in the absence of this keyword is to take the initial iteration as iteration 1.

NOVERSION Turns off the use of version numbers appended to the end of filenames as the method for generating filenames for updated copies of an existing file. The presence of this keyword results in direct use of input file names without a search for the highest available version, and requires the entry of specific output file names in many additional cases. By default, in the absence of this keyword, TINKER generates and attaches version numbers in a manner similar to the Digital OpenVMS operating system. For example, subsequent new versions of the file molecule.xyz would be written first to the filemolecule.xyz_2, then to molecule.xyz_3, etc.

OCTAHEDRON Specifies that the periodic ``box'' is a truncated octahedron with maximal distance across the truncated octahedron as given by the A-AXIS keyword. All other unit cell and periodic box size-defining keywords are ignored if the OCTAHEDRON keyword is present.

OPBEND [2 integers & 1 real] This keyword provides the values for a single Allinger MM-style out-of-plane angle bending potential parameter. The first integer modifier is the atom class of the central trigonal atom and the second integer is the atom class of the out-of-plane atom. The real number modifier gives the force constant value for the out-of-plane angle. The default units for the force constant are kcal/mole/radian², but this can be controlled via the OPBENDUNIT keyword.

OPBENDTERM [NONE/ONLY] This keyword controls use of the Allinger MM-style out-of-plane bending potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

OPBENDUNIT [real] Sets the scale factor needed to convert the energy value computed by the Allinger MM-style out-of-plane bending potential into units of kcal/mole. The correct value is force field dependent and typically provided in the header of the master force field parameter file. The default of (p/180)² = 0.0003046 is used, if the OPBENDUNIT keyword is not given in the force field parameter file or the keyfile.

OPDIST [4 integers & 1 real] This keyword provides the values for a single out-of-plane distance potential parameter. The first integer modifier is the atom class of the central trigonal atom and the three following integer modifiers are the atom classes of the three attached atoms. The real number modifier is the force constant for the harmonic function of the out-of-plane distance of the central atom. The default units for the force constant are kcal/mole/Å², but this can be controlled via the OPDISTUNIT keyword.

OPDISTTERM [NONE/ONLY] This keyword controls use of the out-of-plane distance potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

OPDISTUNIT [real] Sets the scale factor needed to convert the energy value computed by the out-of-plane distance potential into units of kcal/mole. The correct value is force field dependent and typically provided in the header of the master force field parameter file. The default value of 1.0 is used, if the OPDISTUNIT keyword is not given in the force field parameter file or the keyfile.

OVERWRITE Causes TINKER programs, such as minimizations, that output intermediate coordinate sets to create a single disk file for the intermediate results which is successively overwritten with the new intermediate coordinates as they become available. This keyword is essentially the opposite of the SAVECYCLE keyword.

PARAMETERS [file name] Provides the name of the force field parameter file to be used for the current TINKER calculation. The standard file name extension for parameter files, .prm, is an optional part of the file name modifier. The default in the absence of the PARAMETERS keyword is to look for a parameter file with the same base name as the molecular system and ending in the .prm extension. If a valid parameter file is not found, the user will asked to provide a file name interactively.

PIATOM [1 integer & 3 reals] This keyword provides the values for the pisystem MO potential parameters for a single atom class belonging to a pisystem.

PIBOND [2 integers & 2 reals] This keyword provides the values for the pisystem MO potential parameters for a single type of pisystem bond.

PISYSTEM [integer list] This keyword sets the atoms within a molecule that are part of a conjugated p-system. The keyword is followed on the same line by a list of atom numbers and/or atom ranges that constitute the p-system. The Allinger MM force fields use this information to set up an MO calculation used to scale bond and torsion parameters involving p-system atoms.

PITORS [2 integers & 1 real] This keyword provides the values for a single pi-orbital torsional angle potential parameter. The two integer modifiers give the atom class numbers for the atoms involved in the central bond of the torsional angle to be parameterized. The real modifier gives the value of the 2-fold Fourier amplitude for the torsional angle between p-orbitals centered on the defined bond atom classes. The default units for the stretch-torsion force constant can be controlled via the PITORSUNIT keyword.

PITORSTERM [NONE/ONLY] This keyword controls use of the pi-orbital torsional angle potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

PITORSUNIT [real] Sets the scale factor needed to convert the energy value computed by the pi-orbital torsional angle potential into units of kcal/mole. The correct value is force field dependent and typically provided in the header of the master force field parameter file. The default value of 1.0 is used, if the PITORSUNIT keyword is not given in the force field parameter file or the keyfile.

PME-GRID [3 integers] This keyword sets the dimensions of the charge grid used during particle mesh Ewald summation. The three modifiers give the size along the X-, Y- and Z-axes, respectively. If either the Y- or Z-axis dimensions are omitted, then they are set equal to the X-axis dimension. The default in the absence of the PME-GRID keyword is to set the grid size along each axis to the smallest power of 2, 3 and/or 5 which is at least as large as 1.5 times the axis length in Angstoms. Note that the FFT used by PME is not restricted to, but is most efficient for, grid sizes which are powers of 2, 3 and/or 5.

PME-ORDER [integer] This keyword sets the order of the B-spline interpolation used during particle mesh Ewald summation. A default value of 8 is used in the absence of the PME-ORDER keyword.

POLAR-12-SCALE [real] This keyword provides a multiplicative scale factor that is applied to polarization interactions between 1-2 polarization groups, i.e., pairs of atoms that are in directly connected polarization groups. The default value of 0.0 is used, if the POLAR-12-SCALE keyword is not given in either the parameter file or the keyfile.

POLAR-13-SCALE [real] This keyword provides a multiplicative scale factor that is applied to polarization interactions between 1-3 polarization groups, i.e., pairs of atoms that are in polarization groups separated by one other group. The default value of 0.0 is used, if the POLAR-13-SCALE keyword is not given in either the parameter file or the keyfile.

POLAR-14-SCALE [real] This keyword provides a multiplicative scale factor that is applied to polarization interactions between 1-4 polarization groups, i.e., pairs of atoms that are in polarization groups separated by two other groups. The default value of 1.0 is used, if the POLAR-14-SCALE keyword is not given in either the parameter file or the keyfile.

POLAR-15-SCALE [real] This keyword provides a multiplicative scale factor that is applied to polarization interactions between 1-5 polarization groups, i.e., pairs of atoms that are in polarization groups separated by three other groups. The default value of 1.0 is used, if the POLAR-15-SCALE keyword is not given in either the parameter file or the keyfile.

POLAR-DAMP [2 reals] Controls the strength of the damping function applied to induced dipoles and dipole polarization interaction energies. The first modifier sets the radius in Angstoms of a hypothetical atom with unit polarizability, while the second modifier sets the scale factor for the exponent of the damping function. The default values for the radius and the scale factor are 1.662 and 1.0, respectively. Damping is eliminated entirely by using this keyword to set the radius value to zero.

POLAR-EPS [real] This keyword sets the convergence criterion applied during computation of self-consistent induced dipoles. The calculation is deemed to have converged when the rms change (in Debyes) of the induced dipoles at all polarizable sites is less than the value specified with this keyword. The default value in the absence of the keyword is 10^-6 Debyes.

POLAR-OLD This keyword selects the polarization damping scheme used in TINKER 3.8 and earlier. Beginning with the 3.9 release, TINKER implements a short range polarization damping method due to Thole. This option is included primarily to allow continued use of the early TINKER polarizable water model based on the originally implemented flat multiplicative damping.

POLAR-SOR [real] Sets a successive overrelaxation (SOR) factor for use in computation of induced atomic dipoles. Optimal values for this keyword will speed the induced dipole calculation, and poor values can result in convergence failure. The default value in the absence of the POLAR-SOR keyword is 0.7 which often a reasonable value when short-range intramolecular polarization is present. For models lacking intramolecular polarization, keyword values closer to 1.0 may be optimal.

POLARIZATION [DIRECT/MUTUAL] Selects between the use of direct and mutual dipole polarization for force fields that incorporate the polarization term. The DIRECT modifier avoids an iterative calculation by using only the permanent electric field in computation of induced dipoles. The MUTUAL option, which is the default in the absence of the POLARIZATION keyword, iterates the induced dipoles to self-consistency.

POLARIZE [1 integer, 1 real & up to 4 integers] This keyword provides the values for a single atomic dipole polarizability parameter. The integer modifier, if positive, gives the atom type number for which a polarizability parameter is to be defined. If the first integer modifier is negative, then the parameter value to follow applies only to the individual atom whose atom number is the negative of the modifier. The real number modifier gives the value of the dipole polarizability in Å³. The final integer modifiers list the atom type numbers of atoms directly bonded to the current atom and which will be considered to be part of the current atom's polarization group.

POLARIZETERM [NONE/ONLY] This keyword controls use of the atomic dipole polarization potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

POLYMER-CUTOFF [real] Sets the value of an additional cutoff parameter needed for infinite polymer systems. This value must be set to less than half the minimal periodic box dimension and should be greater than the largest possible interatomic distance that can be subject to scaling or exclusion as a local electrostatic or van der Waals interaction. The default in the absence of the POLYMER-CUTOFF keyword is 5.5 Angstroms.

PRINTOUT [integer] A general parameter for iterative procedures such as minimizations that sets the number of iterations between writes of status information to the standard output. The default value in the absence of the keyword is 1, i.e., the calculation status is given every iteration.

RADIUSRULE [ARITHMETIC/GEOMETRIC/CUBIC-MEAN] Sets the functional form of the radius combining rule for heteroatomic van der Waals potential energy interactions. The default in the absence of the RADIUSRULE keyword is to use the arithmetic mean combining rule to get radii for heteroatomic interactions.

RADIUSSIZE [RADIUS/DIAMETER] Determines whether the atom size values given in van der Waals parameters read from VDW keyword statements are interpreted as atomic radius or diameter values. The default in the absence of the RADIUSSIZE keyword is to assume that vdw size parameters are given as radius values.

RADIUSTYPE [R-MIN/SIGMA] Determines whether atom size values given in van der Waals parameters read from VDW keyword statements are interpreted as potential minimum (R_min) or LJ-style sigma (s) values. The default in the absence of the RADIUSTYPE keyword is to assume that vdw size parameters are given as R_min values.

RANDOMSEED [integer] Followed by an integer value, this keyword sets the initial seed value for the random number generator used by TINKER. Setting RANDOMSEED to the same value as an earlier run will allow exact reproduction of the earlier calculation. (Note that this will not hold across different machine types.) RANDOMSEED should be set to a positive integer less than about 2 billion. In the absence of the RANDOMSEED keyword the seed is chosen ``randomly'' based upon the number of seconds that have elapsed in the current decade.

RATTLE [BONDS/ANGLES/DIATOMIC/TRIATOMIC/WATER] Invokes the rattle algorithm, a velocity version of shake, on portions of a molecular system during a molecular dynamic calculation. The RATTLE keyword can be followed by any of the modifiers shown, in which case all occurrences of the modifier species are constrained at ideal values taken from the bond and angle parameters of the force field in use. In the absence of any modifier, RATTLE constrains all bonds to hydrogen atoms at ideal bond lengths.

RATTLE-DISTANCE [2 integers] This keyword allows the use of a ``Rattle'' constraint between the two atoms whose numbers are specified on the keyword line. If the two atoms are involved in a covalent bond, then their distance is constrained to the ideal bond length from the force field. For nonbonded atoms, the rattle constraint is fixed at their distance in the input coordinate file.

REACTIONFIELD [2 reals & 1 integer] This keyword provides parameters needed for the reaction field potential energy calculation. The two real modifiers give the radius of the dielectric cavity and the ratio of the bulk dielectric outside the cavity to that inside the cavity. The integer modifier gives the number of terms in the reaction field summation to be used. In the absence of the REACTIONFIELD keyword, the default values are a cavity of radius 1000000 Å, a dielectric ratio of 80 and use of only the first term of the reaction field summation.

REDUCE [real] Specifies the fraction between zero and one by which the path between starting and final conformational state will be shortened at each major cycle of the transition state location algorithm implemented by the SADDLE program. This causes the path endpoints to move up and out of the terminal structures toward the transition state region. In favorable cases, a nonzero value of the REDUCE modifier can speed convergence to the transition state. The default value in the absence of the REDUCE keyword is zero.

RESTRAIN-ANGLE [3 integers & 3 reals] This keyword implements a flat-welled harmonic potential that can be used to restrain the angle between three atoms to lie within a specified angle range. The integer modifiers contain the atom numbers of the three atoms whose angle is to be restrained. The first real modifier is the force constant in kcal/degree² for the restraint. The last two real modifiers give the lower and upper bounds in degrees on the allowed angle values. If the angle lies between the lower and upper bounds, the restraint potential is zero. Outside the bounds, the harmonic restraint is applied. If the angle range modifiers are omitted, then the atoms are restrained to the angle found in the input structure. If the force constant is also omitted, a default value of 10.0 is used.

RESTRAIN-DISTANCE [2 integers & 3 reals] This keyword implements a flat-welled harmonic potential that can be used to restrain two atoms to lie within a specified distance range. The integer modifiers contain the atom numbers of the two atoms to be restrained. The first real modifier specifies the force constant in kcal/Å² for the restraint. The next two real modifiers give the lower and upper bounds in Ångstroms on the allowed distance range. If the interatomic distance lies between these lower and upper bounds, the restraint potential is zero. Outside the bounds, the harmonic restraint is applied. If the distance range modifiers are omitted, then the atoms are restrained to the interatomic distance found in the input structure. If the force constant is also omitted, a default value of 100.0 is used.

RESTRAIN-GROUPS [2 integers & 3 reals] This keyword implements a flat-welled harmonic distance restraint between the centers-of-mass of two groups of atoms. The integer modifiers are the numbers of the two groups which must be defined separately via the GROUP keyword. The first real modifier is the force constant in kcal/Å² for the restraint. The last two real modifiers give the lower and upper bounds in Ångstroms on the allowed intergroup center-of-mass distance values. If the distance range modifiers are omitted, then the groups are restrained to the distance found in the input structure. If the force constant is also omitted, a default value of 100.0 is used.

RESTRAIN-POSITION [1 integer & 5 reals] This keyword provides the ability to restrain an individual atom to a specified coordinate position. The initial integer modifier contains the atom number of the atom to be restrained. The first real modifier sets the force constant in kcal/Å² for the harmonic restraint potential. The next three real number modifiers give the X-, Y- and Z-coordinates to which the atom is tethered. The final real modifier defines a sphere around the specified coordinates within which the restraint value is zero. If the exclusion sphere radius is omitted, it is taken to be zero. If the coordinates are omitted, then the atom is restrained to the origin. If the force constant is also omitted, a default value of 100.0 is used.

RESTRAIN-TORSION [4 integers & 3 reals] This keyword implements a flat-welled harmonic potential that can be used to restrain the torsional angle between four atoms to lie within a specified angle range. The initial integer modifiers contains the atom numbers of the four atoms whose torsional angle, computed in the atom order listed, is to be restrained. The first real modifier gives a force constant in kcal/degree² for the restraint. The last two real modifiers give the lower and upper bounds in degrees on the allowed torsional angle values. The angle values given can wrap around across -180 and +180 degrees. Outside the allowed angle range, the harmonic restraint is applied. If the angle range modifiers are omitted, then the atoms are restrained to the torsional angle found in the input structure. If the force constant is also omitted, a default value of 1.0 is used.

RESTRAINTERM [NONE/ONLY] This keyword controls use of the restraint potential energy terms. In the absence of a modifying option, this keyword turns on use of these potentials. The NONE option turns off use of these potential energy terms. The ONLY option turns off all potential energy terms except for these terms.

RXNFIELDTERM [NONE/ONLY] This keyword controls use of the reaction field continuum solvation potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

SADDLEPOINT The presence of this keyword allows Newton-style second derivative-based optimization routine used by NEWTON, NEWTROT and other programs to converge to saddlepoints as well as minima on the potential surface. By default, in the absence of the SADDLEPOINT keyword, checks are applied that prevent convergence to stationary points having directions of negative curvature.

SAVE-CYCLE This keyword causes TINKER programs, such as minimizations, that output intermediate coordinate sets to save each successive set to the next consecutively numbered cycle file. The SAVE-CYCLE keyword is the opposite of the OVERWRITE keyword.

SAVE-FORCE This keyword causes TINKER molecular dynamics calculations to save the values of the force components on each atom to a separate cycle file. These files are written whenever the atomic coordinate snapshots are written during the dynamics run. Each atomic force file name contains as a suffix the cycle number followed by the letter f.

SAVE-INDUCED This keyword causes TINKER molecular dynamics calculations that involve polarizable atomic multipoles to save the values of the induced dipole components on each polarizable atom to a separate cycle file. These files are written whenever the atomic coordinate snapshots are written during the dynamics run. Each induced dipole file name contains as a suffix the cycle number followed by the letter u.

SAVE-VELOCITY This keyword causes TINKER molecular dynamics calculations to save the values of the velocity components on each atom to a separate cycle file. These files are written whenever the atomic coordinate snapshots are written during the dynamics run. Each velocity file name contains as a suffix the cycle number followed by the letter v.

SLOPEMAX [real] This keyword and its modifying value set the maximum allowed size of the ratio between the current and initial projected gradients during the line search phase of conjugate gradient or truncated Newton optimizations. If this ratio exceeds SLOPEMAX, then the initial step size is reduced by a factor of 10. The default value is usually set to 10000.0 when not specified via the SLOPEMAX keyword.

SMOOTHING [DEM/GDA/TOPHAT/STOPHAT] This keyword activates the potential energy smoothing methods. Several variations are available depending on the value of the modifier used: DEM= Diffusion Equation Method with a standard Gaussian kernel; GDA= Gaussian Density Annealing as proposed by the Straub group; TOPHAT= a local DEM-like method using a finite range ``tophat'' kernel; STOPHAT= shifted tophat smoothing.

SOLVATE [ASP/SASA/ONION/STILL/HCT/ACE/GBSA] Use of this keyword during energy calculations with any of the standard force fields turns on a continuum solvation free energy term. Several algorithms are available based on the modifier used: ASP= Eisenberg-McLachlan ASP method using the Wesson-Eisenberg vacuum-to-water parameters; SASA= the Ooi-Scheraga SASA method; ONION= the original 1990 Still ``Onion-shell'' GB/SA method; STILL= the 1997 analytical GB/SA method from Still's group; HCT= the pairwise descreening method of Hawkins, Cramer and Truhlar; ACE= the Analytical Continuum Electrostatics solvation method from the Karplus group; GBSA= equivalent to the STILL modifier. At present, GB/SA-style methods are only valid for force fields that use simple partial charge electrostatics.

SOLVATETERM [NONE/ONLY] This keyword controls use of the macroscopic solvation potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

SPACEGROUP [name] This keyword selects the space group to be used in manipulation of crystal unit cells and asymmetric units. The name option must be chosen from one of the following currently implemented space groups: P1, P1(-), P21, Cc, P21/a, P21/n, P21/c, C2/c, P212121, Pna21, Pn21a, Cmc21, Pccn, Pbcn, Pbca, P41, I41/a, P4(-)21c, P4(-)m2, R3c, P6(3)/mcm, Fm3(-)m, Im3(-)m.

SPHERE [4 reals, or 1 integer & 1 real] This keyword provides an alternative to the ACTIVE and INACTIVE keywords for specification of subsets of active atoms. If four real number modifiers are provided, the first three are taken as X-, Y- and Z-coordinates and the fourth is the radius of a sphere centered at these coordinates. In this case, all atoms within the sphere at the start of the calculation are active throughout the calculation, while all other atoms are inactive. Similarly if one integer and real number are given, an ``active'' sphere with radius set by the real is centered on the system atom with atom number given by the integer modifier. Multiple SPHERE keyword lines can be present in a single keyfile, and the list of active atoms specified by the spheres is cumulative.

STEEPEST-DESCENT This keyword forces the L-BFGS optimization routine used by the MINIMIZE program and other programs to perform steepest descent minimization. This option can be useful in conjunction with small step sizes for following minimum energy paths, but is generally inferior to the L-BFGS default for most optimization purposes.

STEPMAX [real] This keyword and its modifying value set the maximum size of an individual step during the line search phase of conjugate gradient or truncated Newton optimizations. The step size is computed as the norm of the vector of changes in parameters being optimized. The default value depends on the particular TINKER program, but is usually in the range from 1.0 to 5.0 when not specified via the STEPMAX keyword.

STEPMIN [real] This keyword and its modifying value set the minimum size of an individual step during the line search phase of conjugate gradient or truncated Newton optimizations. The step size is computed as the norm of the vector of changes in parameters being optimized. The default value is usually set to about 10^-16 when not specified via the STEPMIN keyword.

STRBND [1 integer & 3 reals] This keyword provides the values for a single stretch-bend cross term potential parameter. The integer modifier gives the atom class number for the central atom of the bond angle involved in stretch-bend interactions. The real number modifiers give the force constant values to be used when the central atom of the angle is attached to 0, 1 or 2 additional hydrogen atoms, respectively. The default units for the stretch-bend force constant are kcal/mole/Å-degree, but this can be controlled via the STRBNDUNIT keyword.

STRBNDTERM [NONE/ONLY] This keyword controls use of the bond stretching-angle bending cross term potential energy. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

STRBNDUNIT [real] Sets the scale factor needed to convert the energy value computed by the bond stretching-angle bending cross term potential into units of kcal/mole. The correct value is force field dependent and typically provided in the header of the master force field parameter file. The default value of 1.0 is used, if the STRBNDUNIT keyword is not given in the force field parameter file or the keyfile.

STRTORS [2 integers & 1 real] This keyword provides the values for a single stretch-torsion cross term potential parameter. The two integer modifiers give the atom class numbers for the atoms involved in the central bond of the torsional angles to be parameterized. The real modifier gives the value of the stretch-torsion force constant for all torsional angles with the defined central bond atom classes. The default units for the stretch-torsion force constant can be controlled via the STRTORUNIT keyword.

STRTORTERM [NONE/ONLY] This keyword controls use of the bond stretching-torsional angle cross term potential energy. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

STRTORUNIT [real] Sets the scale factor needed to convert the energy value computed by the bond stretching-torsional angle cross term potential into units of kcal/mole. The correct value is force field dependent and typically provided in the header of the master force field parameter file. The default value of 1.0 is used, if the STRTORUNIT keyword is not given in the force field parameter file or the keyfile.

TAPER [real] This keyword allows modification of the cutoff windows for nonbonded potential energy interactions. The nonbonded terms are smoothly reduced from their standard value at the beginning of the cutoff window to zero at the far end of the window. The far end of the window is specified via the CUTOFF keyword or its potential function specific variants. The modifier value supplied with the TAPER keyword sets the beginning of the cutoff window. The modifier can be given either as an absolute distance value in Angstroms, or as a fraction between zero and one of the CUTOFF distance. The default value in the absence of the TAPER keyword ranges from 0.65 to 0.9 of the CUTOFF distance depending on the type of potential function. The windows are implemented via polynomial-based switching functions, in some cases combined with energy shifting.

TAU-PRESSURE [real] Sets the coupling time in picoseconds for the Groningen-style pressure bath coupling used to control the system pressure during molecular dynamics calculations. A default value of 2.0 is used for TAU-PRESSURE in the absence of the keyword.

TAU-TEMPERATURE [real] Sets the coupling time in picoseconds for the Groningen-style temperature bath coupling used to control the system temperature during molecular dynamics calculations. A default value of 0.1 is used for TAU-TEMPERATURE in the absence of the keyword.

THERMOSTAT [BERENDSEN/ANDERSEN] This keyword selects a thermostat algorithm for use during molecular dynamics. Two modifiers are available, a Berendsen bath coupling method, and an Andersen stochastic collision method. The default in the absence of the THERMOSTAT keyword is to use the BERENDSEN algorithm.

TORSION [4 integers & up to 6 real/real/integer triples] This keyword provides the values for a single torsional angle parameter. The first four integer modifiers give the atom class numbers for the atoms involved in the torsional angle to be defined. Each of the remaining triples of real/real/integer modifiers give the amplitude, phase offset in degrees and periodicity of a particular torsional function term, respectively. Periodicities through 6-fold are allowed for torsional parameters.

TORSION4 [4 integers & up to 6 real/real/integer triples] This keyword provides the values for a single torsional angle parameter specific to atoms in 4-membered rings. The first four integer modifiers give the atom class numbers for the atoms involved in the torsional angle to be defined. The remaining triples of real number and integer modifiers operate as described above for the TORSION keyword.

TORSION5 [4 integers & up to 6 real/real/integer triples] This keyword provides the values for a single torsional angle parameter specific to atoms in 5-membered rings. The first four integer modifiers give the atom class numbers for the atoms involved in the torsional angle to be defined. The remaining triples of real number and integer modifiers operate as described above for the TORSION keyword.

TORSIONTERM [NONE/ONLY] This keyword controls use of the torsional angle potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

TORSIONUNIT [real] Sets the scale factor needed to convert the energy value computed by the torsional angle potential into units of kcal/mole. The correct value is force field dependent and typically provided in the header of the master force field parameter file. The default value of 1.0 is used, if the TORSIONUNIT keyword is not given in the force field parameter file or the keyfile.

TORTOR [7 integers, then multiple lines of 2 integers and 1 real] This keyword is used to provide the values for a single torsion-torsion parameter. The first five integer modifiers give the atom class numbers for the atoms involved in the two adjacent torsional angles to be defined. The last two integer modifiers contain the number of data grid points that lie along each axis of the torsion-torsion map. For example, this value will be 13 for a 30 degree torsional angle spacing, i.e., 360/30 = 12, but 13 values are required since data values for -180 and +180 degrees must both be supplied. The subsequent lines contain the torsion-torsion map data as the integer values in degrees of each torsional angle and the target energy value in kcal/mole.

TORTORTERM [NONE/ONLY] This keyword controls use of the torsion-torsion potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

TORTORUNIT [real] Sets the scale factor needed to convert the energy value computed by the torsion-torsion potential into units of kcal/mole. The correct value is force field dependent and typically provided in the header of the master force field parameter file. The default value of 1.0 is used, if the TORTORUNIT keyword is not given in the force field parameter file or the keyfile.

TRIAL-DISTANCE [CLASSIC/RANDOM/TRICOR/HAVEL integer/PAIRWISE integer] Sets the method for selection of a trial distance matrix during distance geometry computations. The keyword takes a modifier that selects the method to be used. The HAVEL and PAIRWISE modifiers also require an additional integer value that specifies the number of atoms used in metrization and the percentage of metrization, respectively. The default in the absence of this keyword is to use the PAIRWISE method with 100 percent metrization. Further information on the various methods is given with the description of the TINKER distance geometry program.

TRIAL-DISTRIBUTION [real] Sets the initial value for the mean of the Gaussian distribution used to select trial distances between the lower and upper bounds during distance geometry computations. The value given must be between 0 and 1 which represent the lower and upper bounds respectively. This keyword is rarely needed since TINKER will usually be able to choose a reasonable value by default.

TRUNCATE Causes all distance-based nonbond energy cutoffs to be sharply truncated to an energy of zero at distances greater than the value set by the cutoff keyword(s) without use of any shifting, switching or smoothing schemes. At all distances within the cutoff sphere, the full interaction energy is computed.

UREY-CUBIC [real] Sets the value of the cubic term in the Taylor series expansion form of the Urey-Bradley potential energy. The real number modifier gives the value of the coefficient as a multiple of the quadratic coefficient. The default value in the absence of the UREY-CUBIC keyword is zero; i.e., the cubic Urey-Bradley term is omitted.

UREY-QUARTIC [real] Sets the value of the quartic term in the Taylor series expansion form of the Urey-Bradley potential energy. The real number modifier gives the value of the coefficient as a multiple of the quadratic coefficient. The default value in the absence of the UREY-QUARTIC keyword is zero; i.e., the quartic Urey-Bradley term is omitted.

UREYBRAD [3 integers & 2 reals] This keyword provides the values for a single Urey-Bradley cross term potential parameter. The integer modifiers give the atom class numbers for the three kinds of atoms involved in the angle for which a Urey-Bradley term is to be defined. The real number modifiers give the force constant value for the term and the target value for the 1-3 distance in Å. The default units for the force constant are kcal/mole/Å², but this can be controlled via the UREYUNIT keyword.

UREYTERM [NONE/ONLY] This keyword controls use of the Urey-Bradley potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

UREYUNIT [real] Sets the scale factor needed to convert the energy value computed by the Urey-Bradley potential into units of kcal/mole. The correct value is force field dependent and typically provided in the header of the master force field parameter file. The default value of 1.0 is used, if the UREYUNIT keyword is not given in the force field parameter file or the keyfile.

VDW [1 integer & 3 reals] This keyword provides values for a single van der Waals parameter. The integer modifier, if positive, gives the atom class number for which vdw parameters are to be defined. Note that vdw parameters are given for atom classes, not atom types. The three real number modifiers give the values of the atom size in Å, homoatomic well depth in kcal/mole, and an optional reduction factor for univalent atoms.

VDW-12-SCALE [real] This keyword provides a multiplicative scale factor that is applied to van der Waals potential interactions between 1-2 connected atoms, i.e., atoms that are directly bonded. The default value of 0.0 is used, if the VDW-12-SCALE keyword is not given in either the parameter file or the keyfile.

VDW-13-SCALE [real] This keyword provides a multiplicative scale factor that is applied to van der Waals potential interactions between 1-3 connected atoms, i.e., atoms separated by two covalent bonds. The default value of 0.0 is used, if the VDW-13-SCALE keyword is not given in either the parameter file or the keyfile.

VDW-14-SCALE [real] This keyword provides a multiplicative scale factor that is applied to van der Waals potential interactions between 1-4 connected atoms, i.e., atoms separated by three covalent bonds. The default value of 1.0 is used, if the VDW-14-SCALE keyword is not given in either the parameter file or the keyfile.

VDW-15-SCALE [real] This keyword provides a multiplicative scale factor that is applied to van der Waals potential interactions between 1-5 connected atoms, i.e., atoms separated by four covalent bonds. The default value of 1.0 is used, if the VDW-15-SCALE keyword is not given in either the parameter file or the keyfile.

VDW-CUTOFF [real] Sets the cutoff distance value in Angstroms for van der Waals potential energy interactions. The energy for any pair of van der Waals sites beyond the cutoff distance will be set to zero. Other keywords can be used to select a smoothing scheme near the cutoff distance. The default cutoff distance in the absence of the VDW-CUTOFF keyword is infinite for nonperiodic systems and 9.0 for periodic systems.

VDW-TAPER [real] This keyword allows modification of the cutoff windows for van der Waals potential energy interactions. It is similar in form and action to the TAPER keyword, except that its value applies only to the vdw potential. The default value in the absence of the VDW-TAPER keyword is to begin the cutoff window at 0.9 of the vdw cutoff distance.

VDW14 [1 integer & 2 reals] This keyword provides values for a single van der Waals parameter for use in 1-4 nonbonded interactions. The integer modifier, if positive, gives the atom class number for which vdw parameters are to be defined. Note that vdw parameters are given for atom classes, not atom types. The two real number modifiers give the values of the atom size in Å and the homoatomic well depth in kcal/mole. Reduction factors, if used, are carried over from the VDW keyword for the same atom class.

VDWPR [2 integers & 2 reals] This keyword provides the values for the vdw parameters for a single special heteroatomic pair of atoms. The integer modifiers give the pair of atom class numbers for which special vdw parameters are to be defined. The two real number modifiers give the values of the minimum energy contact distance in Å and the well depth at the minimum distance in kcal/mole.

VDWTERM [NONE/ONLY] This keyword controls use of the van der Waals repulsion-dispersion potential energy term. In the absence of a modifying option, this keyword turns on use of the potential. The NONE option turns off use of this potential energy term. The ONLY option turns off all potential energy terms except for this one.

VDWTYPE [LENNARD-JONES / BUCKINGHAM / BUFFERED-14-7 / MM3-HBOND / GAUSSIAN] Sets the functional form for the van der Waals potential energy term. The text modifier gives the name of the functional form to be used. The GAUSSIAN modifier value implements a two or four Gaussian fit to the corresponding Lennard-Jones function for use with potential energy smoothing schemes. The default in the absence of the VDWTYPE keyword is to use the standard two parameter Lennard-Jones function.

VERBOSE Turns on printing of secondary and informational output during a variety of TINKER computations; a subset of the more extensive output provided by the DEBUG keyword.

WALL [real] Sets the radius of a spherical boundary used to maintain droplet boundary conditions. The real modifier specifies the desired approximate radius of the droplet. In practice, an artificial van der Waals wall is constructed at a fixed buffer distance of 2.5 Å outside the specified radius. The effect is that atoms which attempt to move outside the region defined by the droplet radius will be forced toward the center.

WRITEOUT [integer] A general parameter for iterative procedures such as minimizations that sets the number of iterations between writes of intermediate results (such as the current coordinates) to disk file(s). The default value in the absence of the keyword is 1, i.e., the intermediate results are written to file on every iteration. Whether successive intermediate results are saved to new files or replace previously written intermediate results is controlled by the OVERWRITE and SAVE-CYCLE keywords.

8.	Notes on Special Features & Methods

This section contains several short notes with further information about TINKER methodology, algorithms and special features. The discussion is not intended to be exhaustive, but rather to explain features and capabilities so that users can make more complete use of the package.

FILE VERSION NUMBERS

All of the input and output file types routinely used by the TINKER package are capable of existing as multiple versions of a base file name. For example, if the program XYZINT is run on the input file molecule.xyz, the output internal coordinates file will be written to molecule.int. If a file named molecule.int is already present prior to running XYZINT, then the output will be written instead to the next available version, in this case to molecule.int_2. In fact the output is generally written to the lowest available, previously unused version number (molecule.int_3, molecule.int_4, etc., as high as needed). Input file names are handled similarly. If simply molecule or molecule.xyz is entered as the input file name upon running XYZINT, then the highest version of molecule.xyz will be used as the actual input file. If an explicit version number is entered as part of the input file name, then the specified version will be used as the input file.

The version number scheme will be recognized by many older users as a holdover from the VMS origins of the first version of the TINKER software. It has been maintained to make it easier to chain together multiple calculations that may create several new versions of a given file, and to make it more difficult to accidently overwrite a needed result. The version scheme applies to most uses of many common TINKER file types such as .xyz, .int, .key, .arc. It is not used when an overwritten file ``update'' is obviously the correct action, for example, the .dyn molecular dynamics restart files. For those users who prefer a more Unix-like operation, and do not desire use of file versions, this feature can be turned off by adding the NOVERSION keyword to the applicable TINKER keyfile.

The version scheme as implemented in TINKER does have two known quirks. First, it becomes impossible to directly use the original unversioned copy of a file if higher version numbers are present. For example, if the files molecule.xyz and molecule.xyz_2 both exist, then molecule.xyz cannot be accessed as input by XYZINT. If molecule.xyz is entered in response to the input file name question, molecule.xyz_2 (or the highest present version number) will be used as input. The only workaround is to copy or rename molecule.xyz to something else, say molecule.new, and use that name for the input file. Secondly, missing version numbers always end the search for the highest available version number; i.e., version numbers are assumed to be consecutive and without gaps. For example, if molecule.xyz, molecule.xyz_2 and molecule.xyz_4 are present, but not molecule.xyz_3, then molecule.xyz_2 will be used as input to XYZINT if molecule is given as the input file name. Similarly, output files will fill in gaps in an already existing set of file versions.

COMMAND LINE OPTIONS

Many operating systems or compiler supplied-libraries make available something like the standard Unix iargc and getarg routines for capturing command line arguments. On these machines most of the TINKER programs support a selection of command line arguments and options. The name of the keyfile to be used for a calculation is read from the argument following a -k (equivalent to either -key or -keyfile, case insensitive) command line argument. Note that the -k options can appear anywhere on the command line following the executable name. All other command line arguments, excepting the name of the executable program itself, are treated as input arguments. These input arguments are read from left to right and interpreted in order as the answers to questions that would be asked by an interactive invocation of the same TINKER program. For example, the following command line:

newton molecule -k test a a 0.01

will invoke the NEWTON program on the structure file molecule.xyz using the keyfile test.key, automatic mode [a] for both the method and preconditioning, and 0.01 for the RMS gradient per atom termination criterion in kcal/mole/Å. Provided that the force field parameter set, etc. is provided in test.key, the above compuation will procede directly from the command line invocation without further interactive input.

USE ON MICROSOFT WINDOWS SYSTEMS

TINKER executables for Microsoft PC systems should be run from the DOS or Command Prompt window available under the various versions of Windows. The TINKER executable directory should be added to your path via the autoexec.bat file or similar. If using Win2000 or XP, set the number of scrollable lines in the Command Prompt window to a very large number, so that you will be able to inspect screen output after it flies by. With Win95/98, these Command Prompt windows are only able to scroll a small number of lines (amazing!), so TINKER programs which generate large amounts of screen output should be run such that output will be redirected to a file. This can be accomplished by running the TINKER program in batch mode or by using the Unix-like output redirection build into DOS. For example, the command:

dynamic < molecule.inp > molecule.log

will run the TINKER dynamic program taking input from the file molecule.inp and sending output to molecule.log. Also note that command line options as described above are available with the distributed TINKER executables.

Another alternative, particularly attractive to those already familiar with Linux or Unix systems, is to download the Cygwin package currently available under GPL license from the site http://source.redhat.com/cygwin/. The cygwin tools provide many of the GNU tools, including a bash shell window from which TINKER programs can be run.

If the distributed TINKER executables are run directly from Windows by double clicking on the program icon, then the program will run in its own window. However, upon completion of the program the window will close and screen output will be lost. Any output files written by the program will, of course, still be available. The Windows behavior can be changed by adding the EXIT-PAUSE keyword to the keyfile. This keyword causes the executation window to remain open after completion until the ``Enter'' key is pressed.

USE ON APPLE MACINTOSH SYSTEMS

The TINKER executables are best run under Mac OS X in a ``terminal'' application window where behavior is identical to that in a Linux terminal. At present the Force Field Explorer GUI for TINKER will not run on OS X since the required Java3D extensions are unavailable.

We have discontinued active support for Mac OS 9. However, the OS 9 versions of TINKER are run by double clicking on a program icon. The program will run in its own window to which all ``screen'' output will be directed. Upon program termination the window will remain active pending a final return entered by the user which will close the window. Prior to the final return, the contents of the screen window can be saved to a file via the clipboard for permanent storage. Note that Macintosh OS9 uses a colon instead of a forward- or back-slash as the directory separator, so keyfiles transfered from other machines will need to be altered accordingly.

ATOM TYPES VS. ATOM CLASSES

Manipulation of atom types and the proliferation of parameters as atoms are further subdivided into new types is the bane of force field calculation. For example, if each topologically distinct atom arising from the 20 natural amino acids is given a different atom type, then about 300 separate type are required (this ignores the different N- and C-terminal forms of the residues, diastereotopic hydrogens, etc.). However, all these types lead to literally thousands of different force field parameters. In fact, there are many thousands of distinct torsional parameters alone. It is impossible at present to fully optimize each of these parameters; and even if we could, a great many of the parameters would be nearly identical. Two somewhat complimentary solutions are available to handle the proliferation of parameters. The first is to specify the molecular fragments to which a given parameter can be applied in terms of a chemical structure language, SMILES strings for example. Some commercial systems, such as the TRIPOS Sybyl software, make use of such a scheme to parse structures and assign force field parameters.

A second general approach is to use hierarchical cascades of parameter groups. TINKER uses a simple version of this scheme. Each TINKER force field atom has both an atom type number and an atom class number. The types are subsets of the atom classes, i.e., several different atom types can belong to the same atom class. Force field parameters that are somewhat less sensitive to local environment, such as local geometry terms, are then provided and assigned based on atom class. Other energy parameters, such as electrostatic parameters, that are very environment dependent are assigned over the atom types. This greatly reduces the number of independent multiple-atom parameters like the four-atom torsional parameters.

CALCULATIONS ON PARTIAL STRUCTURES

Two methods are available for performing energetic calculations on portions or substructures within a full molecular system. TINKER allows division of the entire system into active and inactive parts which can be defined via keywords. In subsequent calculations, such as minimization or dynamics, only the active portions of the system are allowed to move. The force field engine responds to the active/inactive division by computing all energetic interactions involving at least one active atom; i.e., any interaction whose energy can change with the motion of one or more active atoms is computed.

The second method for partial structure computation involves dividing the original system into a set of atom groups. As before, the groups can be specified via appropriate keywords. The current TINKER implementation allows specification of up to a maximum number of groups as given in the sizes.i dimensioning file. The groups must be disjoint in that no atom can belong to more than one group. Further keywords allow the user to specify which intra- and intergroup sets of energetic interactions will contribute to the total force field energy. Weights for each set of interactions in the total energy can also be input. A specific energetic interaction is assigned to a particular intra- or intergroup set if all the atoms involved in the interaction belong to the group (intra-) or pair of groups (inter-). Interactions involving atoms from more than two groups are not computed.

Note that the groups method and active/inactive method use different assignment procedures for individual interactions. The active/inactive scheme is intended for situations where only a portion of a system is allowed to move, but the total energy needs to reflect the presence of the remaining inactive portion of the structure. The groups method is intended for use in rigid body calculations, and is needed for certain kinds of free energy perturbation calculations.

METAL COMPLEXES AND HYPERVALENT SPECIES

The distribution version of TINKER comes dimensioned for a maximum atomic coordination number of four as needed for standard organic compounds. In order to use TINKER for calculations on species containing higher coordination numbers, simply change the value of the parameter maxval in the master dimensioning file sizes.i and rebuilt the package. Note that this parameter value should not be set larger than necessary since large values can slow the execution of portions of some TINKER programs.

Many molecular mechanics approaches to inorganic and metal structures use an angle bending term which is softer than the usual harmonic bending potential. TINKER implements a Fourier bending term similar to that used by the Landis group's SHAPES force field. The parameters for specific Fourier angle terms are supplied via the ANGLEF parameter and keyword format. Note that a Fourier term will only be used for a particular angle if a corresponding harmonic angle term is not present in the parameter file.

We are now collaborating with Anders Carlsson's group in St. Louis to add his transition metal ligand field term to TINKER. Support for this additional potential functional form is already in the TINKER source code, and we plan to release the energy routines after further testing and parameterization.

NEIGHBOR METHODS FOR NONBONDED TERMS

In addition to standard double loop methods, the Method of Lights is available to speed neighbor searching. This method based on taking intersections of sorted atom lists can be much faster for problems where the cutoff distance is significantly smaller than half the maximal cell dimension. The current version of TINKER does not implement the ``neighbor list'' schemes common to many other simulation packages.

PERIODIC BOUNDARY CONDITIONS

Both spherical cutoff images or replicates of a cell are supported by all TINKER programs that implement periodic boundary conditions. Whenever the cutoff distance is too large for the minimum image to be the only relevant neighbor (i.e., half the minimum box dimension for orthogonal cells), TINKER will automatically switch from the image formalism to use of replicated cells.

DISTANCE CUTOFFS FOR ENERGY FUNCTIONS

Polynomial energy switching over a window is used for terms whose energy is small near the cutoff distance. For monopole electrostatic interactions, which are quite large in typical cutoff ranges, a two polynomial multiplicative-additive shifted energy switch unique to TINKER is applied. The TINKER method is similar in spirit to the force switching methods of Steinbach and Brooks, J. Comput. Chem., 15, 667-683 (1994). While the particle mesh Ewald method is preferred when periodic boundary conditions are present, TINKER's shifted energy switch with reasonable switching windows is quite satisfactory for most routine modeling problems. The shifted energy switch minimizes the perturbation of the energy and the gradient at the cutoff to acceptable levels. Problems should arise only if the property you wish to monitor is known to require explicit inclusion of long range components (i.e., calculation of the dielectric constant, etc.).

EWALD SUMMATION METHODS

TINKER contains a versions of the Ewald summation technique for inclusion of long range electrostatic interactions via periodic boundaries. The particle mesh Ewald (PME) method is available for simple charge-charge potentials, while regular Ewald is provided for polarizable atomic multipole interactions. The accuracy and speed of the regular and PME calculations is dependent on several interrelated parameters. For both methods, the Ewald coefficient and real-space cutoff distance must be set to reasonable and complementary values. Additional control variables for regular Ewald are the fractional coverage and number of vectors used in reciprocal space. For PME the additional control values are the B-spline order and charge grid dimensions. Complete control over all of these parameters is available via the TINKER keyfile mechanism. By default TINKER will select a set of parameters which provide a reasonable compromise between accuracy and speed, but these should be checked and modified as necessary for each individual system.

CONTINUUM SOLVATION MODELS

Several alternative continuum solvation algorithms are contained within TINKER. All of these are accessed via the SOLVATE keyword and its modifiers. Two simple surface area methods are implemented: the ASP method of Eisenberg and McLachlan, and the SASA method from Scheraga's group. These methods are applicable to any of the standard TINKER force fields. Various schemes based on the generalized Born formalism are also available: the original 1990 numerical ``Onion-shell'' GB/SA method from Still's group, the 1997 analytical GB/SA method also due to Still, a pairwise descreening algorithm originally proposed by Hawkins, Cramer and Truhlar, and the analytical continuum solvation (ACE) method of Schaefer and Karplus. At present, the generalized Born methods should only be used with force fields having simple partial charge electrostatic interactions.

Some further comments are in order regarding the GB/SA-style solvation models. The ``Onion-shell'' model is provided mostly for comparison purposes. It uses an exact, analytical surface area calculation for the cavity term and the numerical scheme described in the original paper for the polarization term. This method is very slow, especially for large systems, and does not contain the contribution of the Born radii chain rule term to the first derivatives. We recommend its use only for single-point energy calculations. The other GB/SA methods (``analytical'' Still, H-C-T pairwise descreening, and ACE) use an approximate cavity term based on Born radii, and do contain fully correct derivatives including the Born radii chain rule contribution. These methods all scale in CPU time with the square of the size of the system, and can be used with minimization, molecular dynamics and large molecules.

Finally, we note that the ACE solvation model should not be used with the current version of TINKER. The algorithm is fully implemented in the source code, but parameterization is not complete. As of late 2000, parameter values are only available in the literature for use of ACE with the older CHARMM19 force field. We plan to develop values for use with more modern all-atom force fields, and these will be incorporated into TINKER sometime in the future.

POLARIZABLE MULTIPOLE ELECTROSTATICS

Atomic multipole electrostatics through the quadrupole moment is supported by the current version of TINKER, as is either mutual or direct dipole polarization. Ewald summation is available for inclusion of long range interactions. Calculations are implemented via a mixture of the CCP5 algorithms of W. Smith and the Applequist-Dykstra Cartesian polytensor method. At present analytical energy and Cartesian gradient code is provided.

The TINKER package allows intramolecular polarization to be treated via a version of the interaction damping scheme of Thole. To implement the Thole scheme, it is necessary to set all the mutual-1x-scale keywords to a value of one. The other polarization scaling keyword series, direct-1x-scale and polar-1x-scale, can be set independently to enable a wide variety of polarization models. In order to use an Applequist-style model without polarization damping, simply set the polar-damp keyword to zero.

POTENTIAL ENERGY SMOOTHING

Versions of our Potential Smoothing and Search (PSS) methodology have been implemented within TINKER. This methods belong to the same general family as Scheraga's Diffusion Equation Method, Straub's Gaussian Density Annealing, Shalloway's Packet Annealing and Verschelde's Effective Diffused Potential, but our algorithms reflect our own ongoing research in this area. In many ways the TINKER potential smoothing methods are the deterministic analog of stochastic simulated annealing. The PSS algorithms are very powerful, but are relatively new and are still undergoing modification, testing and calibration within our research group. This version of TINKER also includes a basin-hopping conformational scanning algorithm in the program SCAN which is particularly effective on smoothed potential surfaces.

DISTANCE GEOMETRY METRIZATION

A much improved and very fast random pairwise metrization scheme is available which allows good sampling during trial distance matrix generation without the usual structural anomalies and CPU constraints of other metrization procedures. An outline of the methodology and its application to NMR NOE-based structure refinement is described in the paper by Hodsdon, et al. in J. Mol. Biol., 264, 585-602 (1996). We have obtained good results with something like the keyword phrase trial-distribution pairwise 5, which performs 5% partial random pairwise metrization. For structures over several hundred atoms, a value less than 5 for the percentage of metrization should be fine.

9.	Descriptions of TINKER Routines

The distribution version of the TINKER package contains over 700 separate programs, subroutines and functions. This section contains a brief description of the purpose of most of these code units. Further information can be found in the comments located at the top of each source code file.

ACTIVE Subroutine

"active" sets the list of atoms that are used during each potential energy function calculation

ADDBASE Subroutine

"addbase" builds the Cartesian coordinates for a single nucleic acid base; coordinates are read from the Protein Data Bank file or found from internal coordinates, then atom types are assigned and connectivity data generated

ADDBOND Subroutine

"addbond" adds entries to the attached atoms list in order to generate a direct connection between two atoms

ADDSIDE Subroutine

"addside" builds the Cartesian coordinates for a single amino acid side chain; coordinates are read from the Protein Data Bank file or found from internal coordinates, then atom types are assigned and connectivity data generated

ADJACENT Function

"adjacent" finds an atom connected to atom "i1" other than atom "i2"; if no such atom exists, then the closest atom in space is returned

ALCHEMY Program

"alchemy" computes the free energy difference corresponding to a small perturbation by Boltzmann weighting the potential energy difference over a number of sample states; current version (incorrectly) considers the charge energy to be intermolecular in finding the perturbation energies

ANALYSIS Subroutine

"analysis" calls the series of routines needed to calculate the potential energy and perform energy partitioning analysis in terms of type of interaction or atom number

ANALYZ4 Subroutine

"analyz4" prints the energy to 4 decimal places and number of interactions for each component of the potential energy

ANALYZ6 Subroutine

"analyz6" prints the energy to 6 decimal places and number of interactions for each component of the potential energy

ANALYZ8 Subroutine

"analyz8" prints the energy to 8 decimal places and number of interactions for each component of the potential energy

ANALYZE Program

"analyze" computes and displays the total potential; options are provided to partition the energy by atom or by potential function type; parameters used in computing interactions can also be displayed by atom; output of large energy interactions and of electrostatic and inertial properties is available

ANGLES Subroutine

"angles" finds the total number of bond angles and stores the atom numbers of the atoms defining each angle; for each angle to a trivalent central atom, the third bonded atom is stored for use in out-of-plane bending

ANNEAL Program

"anneal" performs a simulated annealing protocol by means of variable temperature molecular dynamics using either linear, exponential or sigmoidal cooling schedules

ANORM Function

"anorm" finds the norm (length) of a vector; used as a service routine by the Connolly surface area and volume computation

ARCHIVE Program

"archive" is a utility program for coordinate files which concatenates multiple coordinate sets into a single archive file, or extracts individual coordinate sets from an archive

ASET Subroutine

"aset" computes by recursion the A functions used in the evaluation of Slater-type (STO) overlap integrals

ATOMYZE Subroutine

"atomyze" prints the potential energy components broken down by atom and to a choice of precision

ATTACH Subroutine

"attach" generates lists of 1-3, 1-4 and 1-5 connectivities starting from the previously determined list of attached atoms (ie, 1-2 connectivity)

BASEFILE Subroutine

"basefile" extracts from an input filename the portion consisting of any directory name and the base filename

BCUCOF Subroutine

"bcucof" determines the coefficient matrix needed for bicubic interpolation of a function, gradients and cross derivatives

BCUINT Subroutine

"bcuint" performs a bicubic interpolation of the function value on a 2D spline grid

BCUINT1 Subroutine

"bcuint1" performs a bicubic interpolation of the function value and gradient along the directions of a 2D spline grid

BCUINT2 Subroutine

"bcuint2" performs a bicubic interpolation of the function value, gradient and Hessain along the directions of a 2D spline grid

BEEMAN Subroutine

"beeman" performs a single molecular dynamics time step by means of a Beeman multistep recursion formula; the actual coefficients are Brooks' "Better Beeman" values

BETACF Function

"betacf" computes a rapidly convergent continued fraction needed by routine "betai" to evaluate the cumulative Beta distribution

BETAI Function

"betai" evaluates the cumulative Beta distribution function as the probability that a random variable from a distribution with Beta parameters "a" and "b" will be less than "x"

BIGBLOCK Subroutine

"bigblock" replicates the coordinates of a single unit cell to give a larger block of repeated units

BITORS Subroutine

"bitors" finds the total number of bitorsions, pairs of overlapping dihedral angles, and the numbers of the five atoms defining each bitorsion

BMAX Function

"bmax" computes the maximum order of the B functions needed for evaluation of Slater-type (STO) overlap integrals

BNDERR Function

"bnderr" is the distance bound error function and derivatives; this version implements the original and Havel's normalized lower bound penalty, the normalized version is preferred when lower bounds are small (as with NMR NOE restraints), the original penalty is needed if large lower bounds are present

BONDS Subroutine

"bonds" finds the total number of covalent bonds and stores the atom numbers of the atoms defining each bond

BORN Subroutine

"born" computes the Born radius of each atom for use with the various GB/SA solvation models

BORN1 Subroutine

"born1" computes derivatives of the Born radii with respect to atomic coordinates and increments total energy derivatives and virial components for potentials involving Born radii

BOUNDS Subroutine

"bounds" finds the center of mass of each molecule and translates any stray molecules back into the periodic box

BSET Subroutine

"bset" computes by downward recursion the B functions used in the evaluation of Slater-type (STO) overlap integrals

BSPLINE Subroutine

"bspline" calculates the coefficients for an n-th order B-spline approximation

BSPLINE1 Subroutine

"bspline1" calculates the coefficients and derivative coefficients for an n-th order B-spline approximation

BSSTEP Subroutine

"bsstep" takes a single Bulirsch-Stoer step with monitoring of local truncation error to ensure accuracy

CALENDAR Subroutine

"calendar" returns the current time as a set of integer values representing the year, month, day, hour, minute and second

CELLATOM Subroutine

"cellatom" completes the addition of a symmetry related atom to a unit cell by updating the atom type and attachment arrays

CENTER Subroutine

"center" moves the weighted centroid of each coordinate set to the origin during least squares superposition

CERROR Subroutine

"cerror" is the error handling routine for the Connolly surface area and volume computation

CFFTB Subroutine

"cfftb" computes the backward complex discrete Fourier transform, the Fourier synthesis

CFFTB1 Subroutine

CFFTF Subroutine

"cfftf" computes the forward complex discrete Fourier transform, the Fourier analysis

CFFTF1 Subroutine

CFFTI Subroutine

"cffti" initializes the array "wsave" which is used in both forward and backward transforms; the prime factorization of "n" together with a tabulation of the trigonometric functions are computed and stored in "wsave"

CFFTI1 Subroutine

CHIRER Function

"chirer" computes the chirality error and its derivatives with respect to atomic Cartesian coordinates as a sum the squares of deviations of chiral volumes from target values

CHKCLASH Subroutine

"chkclash" determines if there are any atom clashes which might cause trouble on subsequent energy evaluation

CHKPOLE Subroutine

"chkpole" inverts atomic multipole moments as necessary at sites with chiral local reference frame definitions

CHKRING Subroutine

"chkring" tests angles to be constrained for their presence in small rings and removes constraints that are redundant

CHKSIZE Subroutine

"chksize" computes a measure of overall global structural expansion or compaction from the number of excess upper or lower bounds matrix violations

CHKTREE Subroutine

"chktree" tests a minimum energy structure to see if it belongs to the correct progenitor in the existing map

CHKXYZ Subroutine

"chkxyz" finds any pairs of atoms with identical Cartesian coordinates, and prints a warning message

CHOLESKY Subroutine

"cholesky" uses a modified Cholesky method to solve the linear system Ax = b, returning "x" in "b"; "A" is assumed to be a real symmetric positive definite matrix with its diagonal and upper triangle stored by rows

CIRPLN Subroutine

CJKM Function

"cjkm" computes the coefficients of spherical harmonics expressed in prolate spheroidal coordinates

CLIMBER Subroutine

CLIMBRGD Subroutine

CLIMBROT Subroutine

CLIMBTOR Subroutine

CLIMBXYZ Subroutine

CLOCK Subroutine

"clock" determines elapsed CPU time in seconds since the start of the job

CLUSTER Subroutine

"cluster" gets the partitioning of the system into groups and stores a list of the group to which each atom belongs

COLUMN Subroutine

"column" takes the off-diagonal Hessian elements stored as sparse rows and sets up indices to allow column access

COMMAND Subroutine

"command" uses the standard Unix-like iargc/getarg routines to get the number and values of arguments specified on the command line at program runtime

COMPRESS Subroutine

"compress" transfers only the non-buried tori from the temporary tori arrays to the final tori arrays

CONNECT Subroutine

"connect" sets up the attached atom arrays starting from a set of internal coordinates

CONNOLLY Subroutine

"connolly" uses the algorithms from the AMS/VAM programs of Michael Connolly to compute the analytical molecular surface area and volume of a collection of spherical atoms; thus it implements Fred Richards' molecular surface definition as a set of analytically defined spherical and toroidal polygons

CONTACT Subroutine

"contact" constructs the contact surface, cycles and convex faces

CONTROL Subroutine

"control" gets initial values for parameters that determine the output style and information level provided by TINKER

COORDS Subroutine

"coords" converts the three principal eigenvalues/vectors from the metric matrix into atomic coordinates, and calls a routine to compute the rms deviation from the bounds

CORRELATE Program

"correlate" computes the time correlation function of some user-supplied property from individual snapshot frames taken from a molecular dynamics or other trajectory

CREATEJVM Subroutine

CREATESERVER Subroutine

CREATESYSTEM Subroutine

CREATEUPDATE Subroutine

CRYSTAL Program

"crystal" is a utility program which converts between fractional and Cartesian coordinates, and can generate full unit cells from asymmetric units

CUTOFFS Subroutine

"cutoffs" initializes and stores spherical energy cutoff distance windows, Hessian element and Ewald sum cutoffs, and the pairwise neighbor generation method

CYTSY Subroutine

"cytsy" solves a system of linear equations for a cyclically tridiagonal, symmetric, positive definite matrix

CYTSYP Subroutine

"cytsyp" finds the Cholesky factors of a cyclically tridiagonal symmetric, positive definite matrix given by two vectors

CYTSYS Subroutine

"cytsys" solves a cyclically tridiagonal linear system given the Cholesky factors

D1D2 Function

"d1d2" is a utility function used in computation of the reaction field recursive summation elements

DELETE Subroutine

"delete" removes a specified atom from the Cartesian coordinates list and shifts the remaining atoms

DEPTH Function

DESTROYJVM Subroutine

DESTROYSERVER Subroutine

DFTMOD Subroutine

"dftmod" computes the modulus of the discrete Fourier transform of "bsarray", storing it into "bsmod"

DIAGQ Subroutine

"diagq" is a matrix diagonalization routine which is derived from the classical given, housec, and eigen algorithms with several modifications to increase the efficiency and accuracy

DIFFEQ Subroutine

"diffeq" performs the numerical integration of an ordinary differential equation using an adaptive stepsize method to solve the corresponding coupled first-order equations of the general form dyi/dx = f(x,y1,...,yn) for yi = y1,...,yn

DIFFUSE Program

"diffuse" finds the self-diffusion constant for a homogeneous liquid via the Einstein relation from a set of stored molecular dynamics frames; molecular centers of mass are unfolded and mean squared displacements are computed versus time separation

DIST2 Function

"dist2" finds the distance squared between two points; used as a service routine by the Connolly surface area and volume computation

DISTGEOM Program

"distgeom" uses a metric matrix distance geometry procedure to generate structures with interpoint distances that lie within specified bounds, with chiral centers that maintain chirality, and with torsional angles restrained to desired values; the user also has the ability to interactively inspect and alter the triangle smoothed bounds matrix prior to embedding

DMDUMP Subroutine

"dmdump" puts the distance matrix of the final structure into the upper half of a matrix, the distance of each atom to the centroid on the diagonal, and the individual terms of the bounds errors into the lower half of the matrix

DOCUMENT Program

"document" generates a formatted description of all the code modules or common blocks, an index of routines called by each source code module, a listing of all valid keywords, a list of include file dependencies as needed by a Unix-style Makefile, or a formatted force field parameter set summary

DOT Function

"dot" finds the dot product of two vectors

DSTMAT Subroutine

"dstmat" selects a distance matrix containing values between the previously smoothed upper and lower bounds; the distance values are chosen from uniform distributions, in a triangle correlated fashion, or using random partial metrization

DYNAMIC Program

"dynamic" computes a molecular dynamics trajectory in any of several statistical mechanical ensembles with optional periodic boundaries and optional coupling to temperature and pressure baths alternatively a stochastic dynamics trajectory can be generated

EANGANG Subroutine

"eangang" calculates the angle-angle potential energy

EANGANG1 Subroutine

"eangang1" calculates the angle-angle potential energy and first derivatives with respect to Cartesian coordinates

EANGANG2 Subroutine

"eangang2" calculates the angle-angle potential energy second derivatives with respect to Cartesian coordinates using finite difference methods

EANGANG2A Subroutine

"eangang2a" calculates the angle-angle first derivatives for a single interaction with respect to Cartesian coordinates; used in computation of finite difference second derivatives

EANGANG3 Subroutine

"eangang3" calculates the angle-angle potential energy; also partitions the energy among the atoms

EANGLE Subroutine

"eangle" calculates the angle bending potential energy; projected in-plane angles at trigonal centers or Fourier angle bending terms are optionally used

EANGLE1 Subroutine

"eangle1" calculates the angle bending potential energy and the first derivatives with respect to Cartesian coordinates; projected in-plane angles at trigonal centers or Fourier angle bending terms are optionally used

EANGLE2 Subroutine

"eangle2" calculates second derivatives of the angle bending energy for a single atom using a mixture of analytical and finite difference methods; projected in-plane angles at trigonal centers or Fourier angle bending terms are optionally used

EANGLE2A Subroutine

"eangle2a" calculates bond angle bending potential energy second derivatives with respect to Cartesian coordinates

EANGLE2B Subroutine

"eangle2b" computes projected in-plane bending first derivatives for a single angle with respect to Cartesian coordinates; used in computation of finite difference second derivatives

EANGLE3 Subroutine

"eangle3" calculates the angle bending potential energy, also partitions the energy among the atoms; projected in-plane angles at trigonal centers or Fourier angle bending terms are optionally used

EBOND Subroutine

"ebond" calculates the bond stretching energy

EBOND1 Subroutine

"ebond1" calculates the bond stretching energy and first derivatives with respect to Cartesian coordinates

EBOND2 Subroutine

"ebond2" calculates second derivatives of the bond stretching energy for a single atom at a time

EBOND3 Subroutine

"ebond3" calculates the bond stretching energy; also partitions the energy among the atoms

EBUCK Subroutine

"ebuck" calculates the Buckingham exp-6 van der Waals energy

EBUCK0A Subroutine

"ebuck0a" calculates the Buckingham exp-6 van der Waals energy using a pairwise double loop

EBUCK0B Subroutine

"ebuck0b" calculates the Buckingham exp-6 van der Waals energy using the method of lights to locate neighboring atoms

EBUCK0C Subroutine

"ebuck0c" calculates the Buckingham exp-6 van der Waals energy via a Gaussian approximation for potential energy smoothing

EBUCK1 Subroutine

"ebuck1" calculates the Buckingham exp-6 van der Waals energy and its first derivatives with respect to Cartesian coordinates

EBUCK1A Subroutine

"ebuck1a" calculates the Buckingham exp-6 van der Waals energy and its first derivatives using a pairwise double loop

EBUCK1B Subroutine

"ebuck1b" calculates the Buckingham exp-6 van der Waals energy and its first derivatives using the method of lights to locate neighboring atoms

EBUCK1C Subroutine

"ebuck1c" calculates the Buckingham exp-6 van der Waals energy and its first derivatives via a Gaussian approximation for potential energy smoothing

EBUCK2 Subroutine

"ebuck2" calculates the Buckingham exp-6 van der Waals second derivatives for a single atom at a time

EBUCK2A Subroutine

"ebuck2a" calculates the Buckingham exp-6 van der Waals second derivatives using a double loop over relevant atom pairs

EBUCK2B Subroutine

"ebuck2b" calculates the Buckingham exp-6 van der Waals second derivatives via a Gaussian approximation for use with potential energy smoothing

EBUCK3 Subroutine

"ebuck3" calculates the Buckingham exp-6 van der Waals energy and partitions the energy among the atoms

EBUCK3A Subroutine

"ebuck3a" calculates the Buckingham exp-6 van der Waals energy and partitions the energy among the atoms using a pairwise double loop

EBUCK3B Subroutine

"ebuck3b" calculates the Buckingham exp-6 van der Waals energy and also partitions the energy among the atoms using the method of lights to locate neighboring atoms

EBUCK3C Subroutine

"ebuck3c" calculates the Buckingham exp-6 van der Waals energy via a Gaussian approximation for potential energy smoothing

ECHARGE Subroutine

"echarge" calculates the charge-charge interaction energy

ECHARGE0A Subroutine

"echarge0a" calculates the charge-charge interaction energy using a pairwise double loop

ECHARGE0B Subroutine

"echarge0b" calculates the charge-charge interaction energy using the method of lights to locate neighboring atoms

ECHARGE0C Subroutine

"echarge0c" calculates the charge-charge interaction energy for use with potential smoothing methods

ECHARGE0D Subroutine

"echarge0d" calculates the charge-charge interaction energy using a particle mesh Ewald summation

ECHARGE0E Subroutine

"echarge0e" calculates the charge-charge interaction energy using a particle mesh Ewald summation and the method of lights to locate neighboring atoms

ECHARGE1 Subroutine

"echarge1" calculates the charge-charge interaction energy and first derivatives with respect to Cartesian coordinates

ECHARGE1A Subroutine

"echarge1a" calculates the charge-charge interaction energy and first derivatives with respect to Cartesian coordinates using a pairwise double loop

ECHARGE1B Subroutine

"echarge1b" calculates the charge-charge interaction energy and first derivatives with respect to Cartesian coordinates using the method of lights to locate neighboring atoms

ECHARGE1C Subroutine

"echarge1c" calculates the charge-charge interaction energy and first derivatives with respect to Cartesian coordinates for use with potential smoothing methods

ECHARGE1D Subroutine

"echarge1d" calculates the charge-charge interaction energy and first derivatives with respect to Cartesian coordinates using a particle mesh Ewald summation

ECHARGE2 Subroutine

"echarge2" calculates second derivatives of the charge-charge interaction energy for a single atom

ECHARGE2A Subroutine

"echarge2a" calculates second derivatives of the charge-charge interaction energy for a single atom using a pairwise double loop

ECHARGE2B Subroutine

"echarge2b" calculates second derivatives of the charge-charge interaction energy for a single atom for use with potential smoothing methods

ECHARGE2C Subroutine

"echarge2c" calculates second derivatives of the charge-charge interaction energy for a single atom using a particle mesh Ewald summation

ECHARGE3 Subroutine

"echarge3" calculates the charge-charge interaction energy and partitions the energy among the atoms

ECHARGE3A Subroutine

"echarge3a" calculates the charge-charge interaction energy and partitions the energy among the atoms using a pairwise double loop

ECHARGE3B Subroutine

"echarge3b" calculates the charge-charge interaction energy and partitions the energy among the atoms using the method of lights to locate neighboring atoms

ECHARGE3C Subroutine

"echarge3c" calculates the charge-charge interaction energy and partitions the energy among the atoms for use with potential smoothing methods

ECHARGE3D Subroutine

"echarge3d" calculates the charge-charge interaction energy and partitions the energy among the atoms using a particle mesh Ewald summation

ECHARGE3E Subroutine

"echarge3e" calculates the charge-charge interaction energy and partitions the energy among the atoms using a particle mesh Ewald summation and the method of lights to locate neighboring atoms

ECHGDPL Subroutine

"echgdpl" calculates the charge-dipole interaction energy

ECHGDPL1 Subroutine

"echgdpl1" calculates the charge-dipole interaction energy and first derivatives with respect to Cartesian coordinates

ECHGDPL2 Subroutine

"echgdpl2" calculates second derivatives of the charge-dipole interaction energy for a single atom

ECHGDPL3 Subroutine

"echgdpl3" calculates the charge-dipole interaction energy; also partitions the energy among the atoms

EDIPOLE Subroutine

"edipole" calculates the dipole-dipole interaction energy

EDIPOLE1 Subroutine

"edipole1" calculates the dipole-dipole interaction energy and first derivatives with respect to Cartesian coordinates

EDIPOLE2 Subroutine

"edipole2" calculates second derivatives of the dipole-dipole interaction energy for a single atom

EDIPOLE3 Subroutine

"edipole3" calculates the dipole-dipole interaction energy; also partitions the energy among the atoms

EGAUSS Subroutine

"egauss" calculates the Gaussian expansion van der Waals interaction energy

EGAUSS0A Subroutine

"egauss0a" calculates the Gaussian expansion van der Waals interaction energy using a pairwise double loop

EGAUSS0B Subroutine

"egauss0b" calculates the Gaussian expansion van der Waals interaction energy for use with potential energy smoothing

EGAUSS1 Subroutine

"egauss1" calculates the Gaussian expansion van der Waals interaction energy and its first derivatives with respect to Cartesian coordinates

EGAUSS1A Subroutine

"egauss1a" calculates the Gaussian expansion van der Waals interaction energy and its first derivatives using a pairwise double loop

EGAUSS1B Subroutine

"egauss1b" calculates the Gaussian expansion van der Waals interaction energy and its first derivatives for use with stophat potential energy smoothing

EGAUSS2 Subroutine

"egauss2" calculates the Gaussian expansion van der Waals second derivatives for a single atom at a time

EGAUSS2A Subroutine

"egauss2a" calculates the Gaussian expansion van der Waals second derivatives using a pairwise double loop

EGAUSS2B Subroutine

"egauss2b" calculates the Gaussian expansion van der Waals second derivatives for stophat potential energy smoothing

EGAUSS3 Subroutine

"egauss3" calculates the Gaussian expansion van der Waals interaction energy and partitions the energy among the atoms

EGAUSS3A Subroutine

"egauss3a" calculates the Gaussian expansion van der Waals interaction energy and partitions the energy among the atoms using a pairwise double loop

EGAUSS3B Subroutine

"egauss3b" calculates the Gaussian expansion van der Waals interaction energy and partitions the energy among the atoms using a pairwise double loop

EGBSA0A Subroutine

"egbsa0a" calculates the generalized Born polarization energy for the GB/SA solvation models

EGBSA0B Subroutine

"egbsa0b" calculates the generalized Born polarization energy for the GB/SA solvation models for use with potential smoothing methods via analogy to the smoothing of Coulomb's law

EGBSA1A Subroutine

"egbsa1a" calculates the generalized Born energy and first derivatives of the GB/SA solvation models

EGBSA1B Subroutine

"egbsa1b" calculates the generalized Born energy and first derivatives of the GB/SA solvation models for use with potential smoothing methods

EGBSA2A Subroutine

"egbsa2a" calculates second derivatives of the generalized Born energy term for the GB/SA solvation models

EGBSA2B Subroutine

"egbsa2b" calculates second derivatives of the generalized Born energy term for the GB/SA solvation models for use with potential smoothing methods

EGBSA3A Subroutine

"egbsa3a" calculates the generalized Born energy term for the GB/SA solvation models; also partitions the energy among the atoms

EGBSA3B Subroutine

"egbsa3b" calculates the generalized Born polarization energy for the GB/SA solvation models for use with potential smoothing methods via analogy to the smoothing of Coulomb's law; also partitions the energy among the atoms

EGEOM Subroutine

"egeom" calculates the energy due to restraints on positions, distances, angles and torsions as well as Gaussian basin and spherical droplet restraints

EGEOM1 Subroutine

"egeom1" calculates the energy and first derivatives with respect to Cartesian coordinates due to restraints on positions, distances, angles and torsions as well as Gaussian basin and spherical droplet restraints

EGEOM2 Subroutine

"egeom2" calculates second derivatives of restraints on positions, distances, angles and torsions as well as Gaussian basin and spherical droplet restraints

EGEOM3 Subroutine

"egeom3" calculates the energy due to restraints on positions, distances, angles and torsions as well as Gaussian basin and droplet restraints; also partitions energy among the atoms

EHAL Subroutine

"ehal" calculates the buffered 14-7 van der Waals energy

EHAL0A Subroutine

"ehal0a" calculates the buffered 14-7 van der Waals energy using a pairwise double loop

EHAL0B Subroutine

"ehal0a" calculates the buffered 14-7 van der Waals energy using the method of lights to locate neighboring atoms

EHAL1 Subroutine

"ehal1" calculates the buffered 14-7 van der Waals energy and its first derivatives with respect to Cartesian coordinates

EHAL1A Subroutine

"ehal1a" calculates the buffered 14-7 van der Waals energy and its first derivatives with respect to Cartesian coordinates using a pairwise double loop

EHAL1B Subroutine

"ehal1b" calculates the buffered 14-7 van der Waals energy and its first derivatives with respect to Cartesian coordinates using the method of lights to locate neighboring atoms

EHAL2 Subroutine

"ehal2" calculates the buffered 14-7 van der Waals second derivatives for a single atom at a time

EHAL3 Subroutine

"ehal3" calculates the buffered 14-7 van der Waals energy and partitions the energy among the atoms

EHAL3A Subroutine

"ehal3a" calculates the buffered 14-7 van der Waals energy and partitions the energy among the atoms using a pairwise double loop

EHAL3B Subroutine

"ehal3b" calculates the buffered 14-7 van der Waals energy and also partitions the energy among the atoms using the method of lights to locate neighboring atoms

EIGEN Subroutine

"eigen" uses the power method to compute the largest eigenvalues and eigenvectors of the metric matrix, "valid" is set true if the first three eigenvalues are positive

EIGENRGD Subroutine

EIGENROT Subroutine

EIGENTOR Subroutine

EIGENXYZ Subroutine

EIMPROP Subroutine

"eimprop" calculates the improper dihedral potential energy

EIMPROP1 Subroutine

"eimprop1" calculates improper dihedral energy and its first derivatives with respect to Cartesian coordinates

EIMPROP2 Subroutine

"eimprop2" calculates second derivatives of the improper dihedral angle energy for a single atom

EIMPROP3 Subroutine

"eimprop3" calculates the improper dihedral potential energy; also partitions the energy terms among the atoms

EIMPTOR Subroutine

"eimptor" calculates the improper torsion potential energy

EIMPTOR1 Subroutine

"eimptor1" calculates improper torsion energy and its first derivatives with respect to Cartesian coordinates

EIMPTOR2 Subroutine

"eimptor2" calculates second derivatives of the improper torsion energy for a single atom

EIMPTOR3 Subroutine

"eimptor3" calculates the improper torsion potential energy; also partitions the energy terms among the atoms

ELJ Subroutine

"elj" calculates the Lennard-Jones 6-12 van der Waals energy

ELJ0A Subroutine

"elj0a" calculates the Lennard-Jones 6-12 van der Waals energy using a pairwise double loop

ELJ0B Subroutine

"elj0b" calculates the Lennard-Jones 6-12 van der Waals energy using the method of lights to locate neighboring atoms

ELJ0C Subroutine

"elj0c" calculates the Lennard-Jones 6-12 van der Waals energy via a Gaussian approximation for potential energy smoothing

ELJ0D Subroutine

"elj0d" calculates the Lennard-Jones 6-12 van der Waals energy for use with stophat potential energy smoothing

ELJ1 Subroutine

"elj1" calculates the Lennard-Jones 6-12 van der Waals energy and its first derivatives with respect to Cartesian coordinates

ELJ1A Subroutine

"elj1a" calculates the Lennard-Jones 6-12 van der Waals energy and its first derivatives using a pairwise double loop

ELJ1B Subroutine

"elj1b" calculates the Lennard-Jones 6-12 van der Waals energy and its first derivatives using the method of lights to locate neighboring atoms

ELJ1C Subroutine

"elj1c" calculates the Lennard-Jones 6-12 van der Waals energy and its first derivatives via a Gaussian approximation for potential energy smoothing

ELJ1D Subroutine

"elj1d" calculates the van der Waals interaction energy and its first derivatives for use with stophat potential energy smoothing

ELJ2 Subroutine

"elj2" calculates the Lennard-Jones 6-12 van der Waals second derivatives for a single atom at a time

ELJ2A Subroutine

"elj2a" calculates the Lennard-Jones 6-12 van der Waals second derivatives using a double loop over relevant atom pairs

ELJ2B Subroutine

"elj2b" calculates the Lennard-Jones 6-12 van der Waals second derivatives via a Gaussian approximation for use with potential energy smoothing

ELJ2C Subroutine

"elj2c" calculates the Lennard-Jones 6-12 van der Waals second derivatives for use with stophat potential energy smoothing

ELJ3 Subroutine

"elj3" calculates the Lennard-Jones 6-12 van der Waals energy and also partitions the energy among the atoms

ELJ3A Subroutine

"elj3a" calculates the Lennard-Jones 6-12 van der Waals energy and also partitions the energy among the atoms using a pairwise double loop

ELJ3B Subroutine

"elj3b" calculates the Lennard-Jones 6-12 van der Waals energy and also partitions the energy among the atoms using the method of lights to locate neighboring atoms

ELJ3C Subroutine

"elj3c" calculates the Lennard-Jones 6-12 van der Waals energy and also partitions the energy among the atoms via a Gaussian approximation for potential energy smoothing

ELJ3D Subroutine

"elj3d" calculates the Lennard-Jones 6-12 van der Waals energy and also partitions the energy among the atoms for use with stophat potential energy smoothing

EMBED Subroutine

"embed" is a distance geometry routine patterned after the ideas of Gordon Crippen, Irwin Kuntz and Tim Havel; it takes as input a set of upper and lower bounds on the interpoint distances, chirality restraints and torsional restraints, and attempts to generate a set of coordinates that satisfy the input bounds and restraints

EMETAL Subroutine

"emetal" calculates the transition metal ligand field energy

EMETAL1 Subroutine

"emetal1" calculates the transition metal ligand field energy and its first derivatives with respect to Cartesian coordinates

EMETAL2 Subroutine

"emetal2" calculates the transition metal ligand field second derivatives for a single atom at a time

EMETAL3 Subroutine

"emetal3" calculates the transition metal ligand field energy and also partitions the energy among the atoms

EMM3HB Subroutine

"emm3hb" calculates the MM3 exp-6 van der Waals and directional charge transfer hydrogen bonding energy

EMM3HB0A Subroutine

"emm3hb0a" calculates the MM3 exp-6 van der Waals and directional charge transfer hydrogen bonding energy using a pairwise double loop

EMM3HB0B Subroutine

"emm3hb0b" calculates the MM3 exp-6 van der Waals and directional charge transfer hydrogen bonding energy using the method of lights to locate neighboring atoms

EMM3HB1 Subroutine

"emm3hb1" calculates the MM3 exp-6 van der Waals and directional charge transfer hydrogen bonding energy with respect to Cartesian coordinates

EMM3HB1A Subroutine

"emm3hb1a" calculates the MM3 exp-6 van der Waals and directional charge transfer hydrogen bonding energy with respect to Cartesian coordinates using a pairwise double loop

EMM3HB1B Subroutine

"emm3hb1b" calculates the MM3 exp-6 van der Waals and directional charge transfer hydrogen bonding energy with respect to Cartesian coordinates using the method of lights to locate neighboring atoms

EMM3HB2 Subroutine

"emm3hb2" calculates the MM3 exp-6 van der Waals and directional charge transfer hydrogen bonding second derivatives for a single atom at a time

EMM3HB3 Subroutine

"emm3hb3" calculates the MM3 exp-6 van der Waals and directional charge transfer hydrogen bonding energy, and partitions the energy among the atoms

EMM3HB3A Subroutine

"emm3hb3" calculates the MM3 exp-6 van der Waals and directional charge transfer hydrogen bonding energy, and partitions the energy among the atoms

EMM3HB3B Subroutine

"emm3hb3b" calculates the MM3 exp-6 van der Waals and directional charge transfer hydrogen bonding energy using the method of lights to locate neighboring atoms

EMPOLE Subroutine

"empole" calculates the electrostatic energy due to atomic multipole interactions and dipole polarizability

EMPOLE0A Subroutine

"empole0a" calculates the electrostatic energy due to atomic multipole interactions and dipole polarizability using a pairwise double loop

EMPOLE0B Subroutine

"empole0b" calculates the electrostatic energy due to atomic multipole interactions and dipole polarizability using a regular Ewald summation

EMPOLE1 Subroutine

"empole1" calculates the multipole and dipole polarization energy and derivatives with respect to Cartesian coordinates

EMPOLE1A Subroutine

"empole1a" calculates the multipole and dipole polarization energy and derivatives with respect to Cartesian coordinates using a pairwise double loop

EMPOLE1B Subroutine

"empole1b" calculates the multipole and dipole polarization energy and derivatives with respect to Cartesian coordinates using a regular Ewald summation

EMPOLE2 Subroutine

"empole2" calculates second derivatives of the multipole and dipole polarization energy for a single atom at a time

EMPOLE2A Subroutine

"empole2a" computes multipole and dipole polarization first derivatives for a single atom with respect to Cartesian coordinates; used to get finite difference second derivatives

EMPOLE3 Subroutine

"empole3" calculates the electrostatic energy due to atomic multipole interactions and dipole polarizability, and partitions the energy among the atoms

EMPOLE3A Subroutine

"empole3a" calculates the electrostatic energy due to atomic multipole interactions and dipole polarizability, and partitions the energy among the atoms using a double loop

EMPOLE3B Subroutine

"empole3b" calculates the electrostatic energy due to atomic multipole interactions and dipole polarizability, and partitions the energy among the atoms using a regular Ewald summation

ENERGY Function

"energy" calls the subroutines to calculate the potential energy terms and sums up to form the total energy

ENRGYZE Subroutine

"energyze" is an auxiliary routine for the analyze program that performs the energy analysis and prints the total and intermolecular energies

EOPBEND Subroutine

"eopbend" computes the out-of-plane bend potential energy at trigonal centers via a Wilson-Decius-Cross angle bend

EOPBEND1 Subroutine

"eopbend1" computes the out-of-plane bend potential energy and first derivatives at trigonal centers via a Wilson-Decius-Cross angle bend

EOPBEND2 Subroutine

"eopbend2" calculates second derivatives of the out-of-plane bend energy via a Wilson-Decius-Cross angle bend for a single atom using finite difference methods

EOPBEND2A Subroutine

"eopbend2a" calculates out-of-plane bending first derivatives at a trigonal center via a Wilson-Decius-Cross angle bend; used in computation of finite difference second derivatives

EOPBEND3 Subroutine

"eopbend3" computes the out-of-plane bend potential energy at trigonal centers via a Wilson-Decius-Cross angle bend; also partitions the energy among the atoms

EOPDIST Subroutine

"eopdist" computes the out-of-plane distance potential energy at trigonal centers via the central atom height

EOPDIST1 Subroutine

"eopdist1" computes the out-of-plane distance potential energy and first derivatives at trigonal centers via the central atom height

EOPDIST2 Subroutine

"eopdist2" calculates second derivatives of the out-of-plane distance energy for a single atom via the central atom height

EOPDIST3 Subroutine

"eopdist3" computes the out-of-plane distance potential energy at trigonal centers via the central atom height; also partitions the energy among the atoms

EPITORS Subroutine

"epitors" calculates the pi-orbital torsion potential energy

EPITORS1 Subroutine

"epitors1" calculates the pi-orbital torsion potential energy and first derivatives with respect to Cartesian coordinates

EPITORS2 Subroutine

"epitors2" calculates the second derivatives of the pi-orbital torsion energy for a single atom using finite difference methods

EPITORS2A Subroutine

"epitors2a" calculates the pi-orbital torsion first derivatives; used in computation of finite difference second derivatives

EPITORS3 Subroutine

"epitors3" calculates the pi-orbital torsion potential energy; also partitions the energy terms among the atoms

EPME Subroutine

"epme" computes the reciprocal space energy for a particle mesh Ewald summation over partial charges

EPME1 Subroutine

"epme1" computes the reciprocal space energy and first derivatives for a particle mesh Ewald summation

EPME3 Subroutine

"epme3" computes the reciprocal space energy for a particle mesh Ewald summation over partial charges and prints information about the energy over the charge grid points

EPUCLC Subroutine

EREAL Subroutine

"ereal" evaluates the real space portion of the regular Ewald summation energy due to atomic multipole interactions and dipole polarizability

EREAL1 Subroutine

"ereal1" evaluates the real space portion of the regular Ewald summation energy and gradient due to atomic multipole interactions and dipole polarizability

EREAL3 Subroutine

"ereal3" evaluates the real space portion of the regular Ewald summation energy due to atomic multipole interactions and dipole polarizability and partitions the energy among the atoms

ERECIP Subroutine

"erecip" evaluates the reciprocal space portion of the regular Ewald summation energy due to atomic multipole interactions and dipole polarizability

ERECIP1 Subroutine

"erecip1" evaluates the reciprocal space portion of the regular Ewald summation energy and gradient due to atomic multipole interactions and dipole polarizability

ERECIP3 Subroutine

"erecip3" evaluates the reciprocal space portion of the regular Ewald summation energy due to atomic multipole interactions and dipole polarizability, and prints information about the energy over the reciprocal lattice vectors

ERF Function

"erf" computes a numerical approximation to the value of the error function via a Chebyshev approximation

ERFC Function

"erfc" computes a numerical approximation to the value of the complementary error function via a Chebyshev approximation

ERFCORE Subroutine

"erfcore" evaluates erf(x) or erfc(x) for a real argument x; when called with mode set to 0 it returns erf, a mode of 1 returns erfc; uses rational functions that approximate erf(x) and erfc(x) to at least 18 significant decimal digits

ERFIK Subroutine

"erfik" compute the reaction field energy due to a single pair of atomic multipoles

ERFINV Function

"erfinv" evaluates the inverse of the error function erf for a real argument in the range (-1,1) using a rational function approximation followed by cycles of Newton-Raphson correction

ERXNFLD Subroutine

"erxnfld" calculates the macroscopic reaction field energy arising from a set of atomic multipoles

ERXNFLD1 Subroutine

"erxnfld1" calculates the macroscopic reaction field energy and derivatives with respect to Cartesian coordinates

ERXNFLD2 Subroutine

"erxnfld2" calculates second derivatives of the macroscopic reaction field energy for a single atom at a time

ERXNFLD3 Subroutine

"erxnfld3" calculates the macroscopic reaction field energy, and also partitions the energy among the atoms

ESOLV Subroutine

"esolv" calculates the continuum solvation energy via either the Eisenberg-McLachlan ASP model, Ooi-Scheraga SASA model, various GB/SA methods or the ACE model

ESOLV1 Subroutine

"esolv1" calculates the continuum solvation energy and first derivatives with respect to Cartesian coordinates using either the Eisenberg-McLachlan ASP, Ooi-Scheraga SASA or various GB/SA solvation models

ESOLV2 Subroutine

"esolv2" calculates second derivatives of the continuum solvation energy using either the Eisenberg-McLachlan ASP, Ooi-Scheraga SASA or various GB/SA solvation models

ESOLV3 Subroutine

"esolv3" calculates the continuum solvation energy using either the Eisenberg-McLachlan ASP model, Ooi-Scheraga SASA model, various GB/SA methods or the ACE model; also partitions the energy among the atoms

ESTRBND Subroutine

"estrbnd" calculates the stretch-bend potential energy

ESTRBND1 Subroutine

"estrbnd1" calculates the stretch-bend potential energy and first derivatives with respect to Cartesian coordinates

ESTRBND2 Subroutine

"estrbnd2" calculates the stretch-bend potential energy second derivatives with respect to Cartesian coordinates

ESTRBND3 Subroutine

"estrbnd3" calculates the stretch-bend potential energy; also partitions the energy among the atoms

ESTRTOR Subroutine

"estrtor" calculates the stretch-torsion potential energy

ESTRTOR1 Subroutine

"estrtor1" calculates the stretch-torsion energy and first derivatives with respect to Cartesian coordinates

ESTRTOR2 Subroutine

"estrtor2" calculates the stretch-torsion potential energy second derivatives with respect to Cartesian coordinates

ESTRTOR3 Subroutine

"estrtor3" calculates the stretch-torsion potential energy; also partitions the energy terms among the atoms

ETORS Subroutine

"etors" calculates the torsional potential energy

ETORS0A Subroutine

"etors0a" calculates the torsional potential energy using a standard sum of Fourier terms

ETORS0B Subroutine

"etors0b" calculates the torsional potential energy for use with potential energy smoothing methods

ETORS1 Subroutine

"etors1" calculates the torsional potential energy and first derivatives with respect to Cartesian coordinates

ETORS1A Subroutine

"etors1a" calculates the torsional potential energy and first derivatives with respect to Cartesian coordinates using a standard sum of Fourier terms

ETORS1B Subroutine

"etors1b" calculates the torsional potential energy and first derivatives with respect to Cartesian coordinates for use with potential energy smoothing methods

ETORS2 Subroutine

"etors2" calculates the second derivatives of the torsional energy for a single atom

ETORS2A Subroutine

"etors2a" calculates the second derivatives of the torsional energy for a single atom using a standard sum of Fourier terms

ETORS2B Subroutine

"etors2b" calculates the second derivatives of the torsional energy for a single atom for use with potential energy smoothing methods

ETORS3 Subroutine

"etors3" calculates the torsional potential energy; also partitions the energy among the atoms

ETORS3A Subroutine

"etors3a" calculates the torsional potential energy using a standard sum of Fourier terms and partitions the energy among the atoms

ETORS3B Subroutine

"etors3b" calculates the torsional potential energy for use with potential energy smoothing methods and partitions the energy among the atoms

ETORTOR Subroutine

"etortor" calculates the torsion-torsion potential energy

ETORTOR1 Subroutine

"etortor1" calculates the torsion-torsion energy and first derivatives with respect to Cartesian coordinates

ETORTOR2 Subroutine

"etortor2" calculates the torsion-torsion potential energy second derivatives with respect to Cartesian coordinates

ETORTOR3 Subroutine

"etortor3" calculates the torsion-torsion potential energy; also partitions the energy terms among the atoms

EUREY Subroutine

"eurey" calculates the Urey-Bradley 1-3 interaction energy

EUREY1 Subroutine

"eurey1" calculates the Urey-Bradley interaction energy and its first derivatives with respect to Cartesian coordinates

EUREY2 Subroutine

"eurey2" calculates second derivatives of the Urey-Bradley interaction energy for a single atom at a time

EUREY3 Subroutine

"eurey3" calculates the Urey-Bradley energy; also partitions the energy among the atoms

EWALDCOF Subroutine

"ewaldcof" finds a value of the Ewald coefficient such that all terms beyond the specified cutoff distance will have an value less than a specified tolerance

EXPLORE Subroutine

"explore" uses simulated annealing on an initial crude embedded distance geoemtry structure to refine versus the bound, chirality, planarity and torsional error functions

EXTRA Subroutine

"extra" calculates any additional user defined potential energy contribution

EXTRA1 Subroutine

"extra1" calculates any additional user defined potential energy contribution and its first derivatives

EXTRA2 Subroutine

"extra2" calculates second derivatives of any additional user defined potential energy contribution for a single atom at a time

EXTRA3 Subroutine

"extra3" calculates any additional user defined potential contribution and also partitions the energy among the atoms

FATAL Subroutine

"fatal" terminates execution due to a user request, a severe error or some other nonstandard condition

FFTBACK Subroutine

FFTFRONT Subroutine

FFTSETUP Subroutine

FIELD Subroutine

"field" sets the force field potential energy functions from a parameter file and modifications specified in a keyfile

FINAL Subroutine

"final" performs any final program actions, prints a status message, and then pauses if necessary to avoid closing the execution window

FINDATM Subroutine

"findatm" locates a specific PDB atom name type within a range of atoms from the PDB file, returns zero if the name type was not found

FIXPDB Subroutine

"fixpdb" corrects problems with PDB files by converting residue and atom names to the forms used by TINKER

FRACDIST Subroutine

"fracdist" computes a normalized distribution of the pairwise fractional distances between the smoothed upper and lower bounds

FREEUNIT Function

"freeunit" finds an unopened Fortran I/O unit and returns its numerical value from 1 to 99; the units already assigned to "input" and "iout" (usually 5 and 6) are skipped since they have special meaning as the default I/O units

GAMMLN Function

"gammln" uses a series expansion due to Lanczos to compute the natural logarithm of the Gamma function at "x" in [0,1]

GDA Program

"gda" implements Gaussian Density Annealing (GDA) algorithm for global optimization via simulated annealing

GDA1 Subroutine

GDA2 Function

GDA3 Subroutine

GDASTAT Subroutine

GENDOT Subroutine

"gendot" finds the coordinates of a specified number of surface points for a sphere with the input radius and coordinate center

GEODESIC Subroutine

"geodesic" smooths the upper and lower distance bounds via the triangle inequality using a sparse matrix version of a shortest path algorithm

GEOMETRY Function

"geometry" finds the value of the interatomic distance, angle or dihedral angle defined by two to four input atoms

GETBASE Subroutine

"getbase" finds the base heavy atoms for a single nucleotide residue and copies the names and coordinates to the Protein Data Bank file

GETIME Subroutine

"getime" gets elapsed CPU time in seconds for an interval

GETINT Subroutine

"getint" asks for an internal coordinate file name, then reads the internal coordinates and computes Cartesian coordinates

GETKEY Subroutine

"getkey" finds a valid keyfile and stores its contents as line images for subsequent keyword parameter searching

GETMOL2 Subroutine

"getmol2" asks for a Sybyl MOL2 molecule file name, then reads the coordinates from the file

GETMONITOR Subroutine

GETNUCH Subroutine

"getnuch" finds the nucleotide hydrogen atoms for a single residue and copies the names and coordinates to the Protein Data Bank file

GETNUMB Subroutine

"getnumb" searchs an input string from left to right for an integer and puts the numeric value in "number"; returns zero with "next" unchanged if no integer value is found

GETPDB Subroutine

"getpdb" asks for a Protein Data Bank file name, then reads in the coordinates file

GETPRB Subroutine

"getprb" tests for a possible probe position at the interface between three neighboring atoms

GETPRM Subroutine

"getprm" finds the potential energy parameter file and then opens and reads the parameters

GETPROH Subroutine

"getproh" finds the hydrogen atoms for a single amino acid residue and copies the names and coordinates to the Protein Data Bank file

GETREF Subroutine

"getref" copies structure information from the reference area into the standard variables for the current system structure

GETSEQ Subroutine

"getseq" asks the user for the amino acid sequence and torsional angle values needed to define a peptide

GETSEQN Subroutine

"getseqn" asks the user for the nucleotide sequence and torsional angle values needed to define a nucleic acid

GETSIDE Subroutine

"getside" finds the side chain heavy atoms for a single amino acid residue and copies the names and coordinates to the Protein Data Bank file

GETSTRING Subroutine

"getstring" searchs for a quoted text string within an input character string; the region between the first and second quotes is returned as the "text"; if the actual text is too long, only the first part is returned

GETTEXT Subroutine

"gettext" searchs an input string for the first string of non-blank characters; the region from a non-blank character to the first blank space is returned as "text"; if the actual text is too long, only the first part is returned

GETTOR Subroutine

"gettor" tests for a possible torus position at the interface between two atoms, and finds the torus radius, center and axis

GETWORD Subroutine

"getword" searchs an input string for the first alphabetic character (A-Z or a-z); the region from this first character to the first blank space or comma is returned as a "word"; if the actual word is too long, only the first part is returned

GETXYZ Subroutine

"getxyz" asks for a Cartesian coordinate file name, then reads in the coordinates file

GRADIENT Subroutine

"gradient" calls subroutines to calculate the potential energy and first derivatives with respect to Cartesian coordinates

GRADRGD Subroutine

"gradrgd" calls subroutines to calculate the potential energy and first derivatives with respect to rigid body coordinates

GRADROT Subroutine

"gradrot" calls subroutines to calculate the potential energy and its torsional first derivatives

GRAFIC Subroutine

"grafic" outputs the upper & lower triangles and diagonal of a square matrix in a schematic form for visual inspection

GROUPS Subroutine

"groups" tests a set of atoms to see if all are members of a single atom group or a pair of atom groups; if so, then the correct intra- or intergroup weight is assigned

GRPLINE Subroutine

"grpline" tests each atom group for linearity of the sites contained in the group

GYRATE Subroutine

"gyrate" computes the radius of gyration of a molecular system from its atomic coordinates

HANGLE Subroutine

"hangle" constructs hybrid angle bending parameters given an initial state, final state and "lambda" value

HATOM Subroutine

"hatom" assigns a new atom type to each hybrid site

HBOND Subroutine

"hbond" constructs hybrid bond stretch parameters given an initial state, final state and "lambda" value

HCHARGE Subroutine

"hcharge" constructs hybrid charge interaction parameters given an initial state, final state and "lambda" value

HDIPOLE Subroutine

"hdipole" constructs hybrid dipole interaction parameters given an initial state, final state and "lambda" value

HESSIAN Subroutine

"hessian" calls subroutines to calculate the Hessian elements for each atom in turn with respect to Cartesian coordinates

HESSRGD Subroutine

"hessrgd" computes the numerical Hessian elements with respect to rigid body coordinates via 6*ngroup+1 gradient evaluations

HESSROT Subroutine

"hessrot" computes the numerical Hessian elements with respect to torsional angles; either the full matrix or just the diagonal can be calculated; the full matrix needs nomega+1 gradient evaluations while the diagonal requires just two gradient calls

HIMPTOR Subroutine

"himptor" constructs hybrid improper torsional parameters given an initial state, final state and "lambda" value

HSTRBND Subroutine

"hstrbnd" constructs hybrid stretch-bend parameters given an initial state, final state and "lambda" value

HSTRTOR Subroutine

"hstrtor" constructs hybrid stretch-torsion parameters given an initial state, final state and "lambda" value

HTORS Subroutine

"htors" constructs hybrid torsional parameters for a given initial state, final state and "lambda" value

HVDW Subroutine

"hvdw" constructs hybrid van der Waals parameters given an initial state, final state and "lambda" value

HYBRID Subroutine

"hybrid" constructs the hybrid hamiltonian for a specified initial state, final state and mutation parameter "lambda"

IJKPTS Subroutine

"ijkpts" stores a set of indices used during calculation of macroscopic reaction field energetics

IMAGE Subroutine

"image" takes the components of pairwise distance between two points in the same or neighboring periodic boxes and converts to the components of the minimum image distance

IMPOSE Subroutine

"impose" performs the least squares best superposition of two atomic coordinate sets via a quaternion method; upon return, the first coordinate set is unchanged while the second set is translated and rotated to give best fit; the final root mean square fit is returned in "rmsvalue"

INDUCE Subroutine

"induce" computes the induced dipole moment at each polarizable site due to direct or mutual polarization; assumes that multipole components have already been rotated into the global coordinate frame

INDUCE0A Subroutine

"induce0a" computes the induced dipole moment at each polarizable site using a pairwise double loop

INDUCE0B Subroutine

"induce0b" computes the induced dipole moment at each polarizable site using a regular Ewald summation

INEDGE Subroutine

"inedge" inserts a concave edge into the linked list for its temporary torus

INERTIA Subroutine

"inertia" computes the principal moments of inertia for the system, and optionally translates the center of mass to the origin and rotates the principal axes onto the global axes

INITERR Function

"initerr" is the initial error function and derivatives for a distance geometry embedding; it includes components from the local geometry and torsional restraint errors

INITIAL Subroutine

"initial" sets up original values for some parameters and variables that might not otherwise get initialized

INITPRM Subroutine

"initprm" completely initializes a force field by setting all parameters to zero and using defaults for control values

INITRES Subroutine

"initres" sets names for biopolymer residue types used in PDB file conversion and automated generation of structures

INITROT Subroutine

"initrot" sets the torsional angles which are to be rotated in subsequent computation, by default automatically selects all rotatable single bonds; assumes internal coordinates have already been setup

INSERT Subroutine

"insert" adds the specified atom to the Cartesian coordinates list and shifts the remaining atoms

INTEDIT Program

"intedit" allows the user to extract information from or alter the values within an internal coordinates file

INTXYZ Program

"intxyz" takes as input an internal coordinates file, converts to and then writes out Cartesian coordinates

INVBETA Function

"invbeta" computes the inverse Beta distribution function via a combination of Newton iteration and bisection search

INVERT Subroutine

"invert" inverts a matrix using the Gauss-Jordan method

IPEDGE Subroutine

"ipedge" inserts convex edge into linked list for atom

ISPLPE Subroutine

"isplpe" computes the coefficients for a cubic periodic interpolating spline

JACOBI Subroutine

"jacobi" performs a matrix diagonalization of a real symmetric matrix by the method of Jacobi rotations

KANGANG Subroutine

"kangang" assigns the parameters for angle-angle cross term interactions and processes new or changed parameter values

KANGLE Subroutine

"kangle" assigns the force constants and ideal angles for the bond angles; also processes new or changed parameters

KATOM Subroutine

"katom" assigns an atom type definitions to each atom in the structure and processes any new or changed values

KBOND Subroutine

"kbond" assigns a force constant and ideal bond length to each bond in the structure and processes any new or changed parameter values

KCHARGE Subroutine

"kcharge" assigns partial charges to the atoms within the structure and processes any new or changed values

KCHIRAL Subroutine

"kchiral" determines the target value for each chirality and planarity restraint as the signed volume of the parallelpiped spanned by vectors from a common atom to each of three other atoms

KDIPOLE Subroutine

"kdipole" assigns bond dipoles to the bonds within the structure and processes any new or changed values

KENEG Subroutine

"keneg" applies primary and secondary electronegativity bond length corrections to applicable bond parameters

KEWALD Subroutine

"kewald" assigns both regular Ewald summation and particle mesh Ewald parameters for a periodic box

KGEOM Subroutine

"kgeom" asisgns parameters for geometric restraint terms to be included in the potential energy calculation

KIMPROP Subroutine

"kimprop" assigns potential parameters to each improper dihedral in the structure and processes any changed values

KIMPTOR Subroutine

"kimptor" assigns torsional parameters to each improper torsion in the structure and processes any changed values

KINETIC Subroutine

"kinetic" computes the total kinetic energy and kinetic energy contributions to the pressure tensor by summing over velocities

KMETAL Subroutine

"kmetal" assigns ligand field parameters to transition metal atoms and processes any new or changed parameter values

KMPOLE Subroutine

"kmpole" assigns atomic multipole moments to the atoms of the structure and processes any new or changed values

KOPBEND Subroutine

"kopbend" assigns the force constants for out-of-plane bending at trigonal centers via Wilson-Decius-Cross angle bends; also processes any new or changed parameter values

KOPDIST Subroutine

"kopdist" assigns the force constants for out-of-plane distance at trigonal centers via the central atom height; also processes any new or changed parameter values

KORBIT Subroutine

"korbit" assigns pi-orbital parameters to conjugated systems and processes any new or changed parameters

KPITORS Subroutine

"kpitors" assigns pi-orbital torsion parameters to torsions needing them, and processes any new or changed values

KPOLAR Subroutine

"kpolar" assigns atomic dipole polarizabilities to the atoms within the structure and processes any new or changed values

KSOLV Subroutine

"ksolv" assigns continuum solvation energy parameters for the Eisenberg-McLachlan ASP, Ooi-Scheraga SASA or various GB/SA solvation models

KSTRBND Subroutine

"kstrbnd" assigns the parameters for the stretch-bend interactions and processes new or changed parameter values

KSTRTOR Subroutine

"kstrtor" assigns stretch-torsion parameters to torsions needing them, and processes any new or changed values

KTORS Subroutine

"ktors" assigns torsional parameters to each torsion in the structure and processes any new or changed values

KTORTOR Subroutine

"ktortor" assigns torsion-torsion parameters to adjacent torsion pairs and processes any new or changed values

KUREY Subroutine

"kurey" assigns the force constants and ideal distances for the Urey-Bradley 1-3 interactions; also processes any new or changed parameter values

KVDW Subroutine

"kvdw" assigns the parameters to be used in computing the van der Waals interactions and processes any new or changed values for these parameters

LATTICE Subroutine

"lattice" stores the periodic box dimensions and sets angle values to be used in computing fractional coordinates

LBFGS Subroutine

"lbfgs" is a limited memory BFGS quasi-newton nonlinear optimization routine

LIGASE Subroutine

"ligase" translates a nucleic acid structure in Protein Data Bank format to a Cartesian coordinate file and sequence file

LIGHTS Subroutine

"lights" computes the set of nearest neighbor interactions using the method of lights algorithm

LINBODY Subroutine

"linbody" finds the angular velocity of a linear rigid body given the inertia tensor and angular momentum

LMSTEP Subroutine

"lmstep" computes the Levenberg-Marquardt step during a nonlinear least squares calculation; this version is based upon ideas from the Minpack routine LMPAR together with with the internal doubling strategy of Dennis and Schnabel

LOCALMIN Subroutine

"localmin" is used during normal mode local search to perform a Cartesian coordinate energy minimization

LOCALRGD Subroutine

"localrgd" is used during the PSS local search procedure to perform a rigid body energy minimization

LOCALROT Subroutine

"localrot" is used during the PSS local search procedure to perform a torsional space energy minimization

LOCALXYZ Subroutine

"localxyz" is used during the potential smoothing and search procedure to perform a local optimization at the current smoothing level

LOCERR Function

"locerr" is the local geometry error function and derivatives including the 1-2, 1-3 and 1-4 distance bound restraints

LOWCASE Subroutine

"lowcase" converts a text string to all lower case letters

MAJORIZE Subroutine

"majorize" refines the projected coordinates by attempting to minimize the least square residual between the trial distance matrix and the distances computed from the coordinates

MAKEINT Subroutine

"makeint" converts Cartesian to internal coordinates where selection of internal coordinates is controlled by "mode"

MAKEPDB Subroutine

"makexyz" converts a set of Cartesian coordinates to Protein Data Bank format with special handling for systems consisting of polypeptide chains, ligands and water molecules

MAKEREF Subroutine

"makeref" copies the information contained in the "xyz" file of the current structure into corresponding reference areas

MAKEXYZ Subroutine

"makexyz" generates a complete set of Cartesian coordinates for a full structure from the internal coordinate values

MAPCHECK Subroutine

"mapcheck" checks the current minimum energy structure for possible addition to the master list of local minima

MAXWELL Function

"maxwell" returns a speed in Angstroms/picosecond randomly selected from a 3-D Maxwell-Boltzmann distribution for the specified particle mass and system temperature

MCM1 Function

"mcm1" is a service routine that computes the energy and gradient for truncated Newton optimization in Cartesian coordinate space

MCM2 Subroutine

"mcm2" is a service routine that computes the sparse matrix Hessian elements for truncated Newton optimization in Cartesian coordinate space

MCMSTEP Function

"mcmstep" implements the minimization phase of an MCM step via Cartesian minimization following a Monte Carlo step

MDINIT Subroutine

"mdinit" initializes the velocities and accelerations for a molecular dynamics trajectory, including restarts

MDREST Subroutine

"mdrest" finds and removes any translational or rotational kinetic energy of the overall system center of mass

MDSAVE Subroutine

"mdsave" writes molecular dynamics trajectory snapshots and auxiliary files with velocity and induced dipole information; also checks for user requested termination of a simulation

MDSTAT Subroutine

"mdstat" is called at each molecular dynamics time step to form statistics on various average values and fluctuations, and to periodically save the state of the trajectory

MEASFN Subroutine

MEASFP Subroutine

MEASFS Subroutine

MEASPM Subroutine

"measpm" computes the volume of a single prism section of the full interior polyhedron

MECHANIC Subroutine

"mechanic" sets up needed parameters for the potential energy calculation and reads in many of the user selectable options

MERGE Subroutine

"merge" combines the reference and current structures into a single new "current" structure containing the reference atoms followed by the atoms of the current structure

METRIC Subroutine

"metric" takes as input the trial distance matrix and computes the metric matrix of all possible dot products between the atomic vectors and the center of mass using the law of cosines and the following formula for the distances to the center of mass:

MIDERR Function

"miderr" is the secondary error function and derivatives for a distance geometry embedding; it includes components from the distance bounds, local geometry, chirality and torsional restraint errors

MINIMIZ1 Function

"minimiz1" is a service routine that computes the energy and gradient for a low storage BFGS optimization in Cartesian coordinate space

MINIMIZE Program

"minimize" performs energy minimization in Cartesian coordinate space using a low storage BFGS nonlinear optimization

MINIROT Program

"minirot" performs an energy minimization in torsional angle space using a low storage BFGS nonlinear optimization

MINIROT1 Function

"minirot1" is a service routine that computes the energy and gradient for a low storage BFGS nonlinear optimization in torsional angle space

MINPATH Subroutine

"minpath" is a routine for finding the triangle smoothed upper and lower bounds of each atom to a specified root atom using a sparse variant of the Bellman-Ford shortest path algorithm

MINRIGID Program

"minrigid" performs an energy minimization of rigid body atom groups using a low storage BFGS nonlinear optimization

MINRIGID1 Function

"minrigid1" is a service routine that computes the energy and gradient for a low storage BFGS nonlinear optimization of rigid bodies

MMID Subroutine

"mmid" implements a modified midpoint method to advance the integration of a set of first order differential equations

MODECART Subroutine

MODEROT Subroutine

MODESRCH Subroutine

MODETORS Subroutine

MODULI Subroutine

"moduli" sets the moduli of the inverse discrete Fourier transform of the B-splines; bsmod[1-3] hold these values, nfft[1-3] are the grid dimensions, bsorder is the order of B-spline approximation

MOLECULE Subroutine

"molecule" counts the molecules, assigns each atom to its molecule and computes the mass of each molecule

MOLUIND Subroutine

"moluind" computes the molecular induced dipole components in the presence of an external electric field

MOMENTS Subroutine

"moments" computes the total electric charge, dipole and quadrupole moments for the entire system as a sum over the partial charges, bond dipoles and atomic multipole moments

MONTE Program

"monte" performs a Monte Carlo/MCM conformational search using either Cartesian single atom or torsional move sets

MUTATE Subroutine

"mutate" constructs the hybrid hamiltonian for a specified initial state, final state and mutation parameter "lambda"

NEEDUPDATE Subroutine

NEIGHBOR Subroutine

"neighbor" finds all of the neighbors of each atom

NEWATM Subroutine

"newatm" creates and defines an atom needed for the Cartesian coordinates file, but which may not present in the original Protein Data Bank file

NEWTON Program

"newton" performs an energy minimization in Cartesian coordinate space using a truncated Newton method

NEWTON1 Function

"newton1" is a service routine that computes the energy and gradient for truncated Newton optimization in Cartesian coordinate space

NEWTON2 Subroutine

"newton2" is a service routine that computes the sparse matrix Hessian elements for truncated Newton optimization in Cartesian coordinate space

NEWTROT Program

"newtrot" performs an energy minimization in torsional angle space using a truncated Newton conjugate gradient method

NEWTROT1 Function

"newtrot1" is a service routine that computes the energy and gradient for truncated Newton conjugate gradient optimization in torsional angle space

NEWTROT2 Subroutine

"newtrot2" is a service routine that computes the sparse matrix Hessian elements for truncated Newton optimization in torsional angle space

NEXTARG Subroutine

"nextarg" finds the next unused command line argument and returns it in the input character string

NEXTTEXT Function

"nexttext" finds and returns the location of the first non-blank character within an input text string; zero is returned if no such character is found

NORMAL Function

"normal" generates a random number from a normal Gaussian distribution with a mean of zero and a variance of one

NUCBASE Subroutine

"nucbase" builds the side chain for a single nucleotide base in terms of internal coordinates

NUCCHAIN Subroutine

"nucchain" builds up the internal coordinates for a nucleic acid sequence from the sugar type, backbone and glycosidic torsional values

NUCLEIC Program

"nucleic" builds the internal and Cartesian coordinates of a polynucleotide from nucleic acid sequence and torsional angle values for the nucleic acid backbone and side chains

NUMBER Function

"number" converts a text numeral into an integer value; the input string must contain only numeric characters

NUMERAL Subroutine

"numeral" converts an input integer number into the corresponding right- or left-justified text numeral

NUMGRAD Subroutine

"numgrad" computes the gradient of the objective function "fvalue" with respect to Cartesian coordinates of the atoms via a two-sided numerical differentiation

OCVM Subroutine

"ocvm" is an optimally conditioned variable metric nonlinear optimization routine without line searches

OLDATM Subroutine

"oldatm" get the Cartesian coordinates for an atom from the Protein Data Bank file, then assigns the atom type and atomic connectivities

OPENEND Subroutine

"openend" opens a file on a Fortran unit such that the position is set to the bottom for appending to the end of the file

OPTIMIZ1 Function

"optimiz1" is a service routine that computes the energy and gradient for optimally conditioned variable metric optimization in Cartesian coordinate space

OPTIMIZE Program

"optimize" performs energy minimization in Cartesian coordinate space using an optimally conditioned variable metric method

OPTIROT Program

"optirot" performs an energy minimization in torsional angle space using an optimally conditioned variable metric method

OPTIROT1 Function

"optirot1" is a service routine that computes the energy and gradient for optimally conditioned variable metric optimization in torsional angle space

OPTRIGID Program

"optrigid" performs an energy minimization of rigid body atom groups using an optimally conditioned variable metric method

OPTRIGID1 Function

"optrigid1" is a service routine that computes the energy and gradient for optimally conditioned variable metric optimization of rigid bodies

OPTSAVE Subroutine

"optsave" is used by the optimizers to write imtermediate coordinates and other relevant information; also checks for user requested termination of an optimization

ORBITAL Subroutine

"orbital" finds and organizes lists of atoms in a pisystem, bonds connecting pisystem atoms and torsions whose two central atoms are both pisystem atoms

ORIENT Subroutine

"orient" computes a set of reference Cartesian coordinates in standard orientation for each rigid body atom group

ORTHOG Subroutine

"orthog" performs an orthogonalization of an input matrix via the modified Gram-Schmidt algorithm

OVERLAP Subroutine

"overlap" computes the overlap for two parallel p-orbitals given the atomic numbers and distance of separation

PARAMYZE Subroutine

"paramyze" prints the force field parameters used in the computation of each of the potential energy terms

PASSB Subroutine

PASSB2 Subroutine

PASSB3 Subroutine

PASSB4 Subroutine

PASSB5 Subroutine

PASSF Subroutine

PASSF2 Subroutine

PASSF3 Subroutine

PASSF4 Subroutine

PASSF5 Subroutine

PATH Program

"path" locates a series of structures equally spaced along a conformational pathway connecting the input reactant and product structures; a series of constrained optimizations orthogonal to the path is done via Lagrangian multipliers

PATH1 Function

PATHPNT Subroutine

"pathpnt" finds a structure on the synchronous transit path with the specified path value "t"

PATHSCAN Subroutine

"pathscan" makes a scan of a synchronous transit pathway by computing structures and energies for specific path values

PATHVAL Subroutine

"pathval" computes the synchronous transit path value for the specified structure

PDBATM Subroutine

"pdbatm" adds an atom to the Protein Data Bank file

PDBXYZ Program

"pdbxyz" takes as input a Protein Data Bank file and then converts to and writes out a Cartesian coordinates file and, for biopolymers, a sequence file

PIALTER Subroutine

"pialter" first modifies bond lengths and force constants according to the standard bond slope parameters and the bond order values stored in "pnpl"; also alters some 2-fold torsional parameters based on the bond-order * beta matrix

PIMOVE Subroutine

"pimove" rotates the vector between atoms "list(1)" and "list(2)" so that atom 1 is at the origin and atom 2 along the x-axis; the atoms defining the respective planes are also moved and their bond lengths normalized

PIPLANE Subroutine

"piplane" selects the three atoms which specify the plane perpendicular to each p-orbital; the current version will fail in certain situations, including ketenes, allenes, and isolated or adjacent triple bonds

PISCF Subroutine

"piscf" performs an scf molecular orbital calculation for the pisystem using a modified Pariser-Parr-Pople method

PITILT Subroutine

"pitilt" calculates for each pibond the ratio of the actual p-orbital overlap integral to the ideal overlap if the same orbitals were perfectly parallel

PLACE Subroutine

"place" finds the probe sites by putting the probe sphere tangent to each triple of neighboring atoms

POLARGRP Subroutine

"polargrp" generates members of the polarization group of each atom and separate lists of the 1-2, 1-3 and 1-4 group connectivities

POLARIZE Program

"polarize" computes the molecular polarizability by applying an external field along each axis followed by diagonalization of the resulting polarizability tensor

POLYMER Subroutine

"polymer" tests for the presence of an infinite polymer extending across periodic boundaries

POLYP Subroutine

"polyp" is a polynomial product routine that multiplies two algebraic forms

POTNRG Function

POTOFF Subroutine

"potoff" clears the forcefield definition by turning off the use of each of the potential energy functions

POWER Subroutine

"power" uses the power method with deflation to compute the few largest eigenvalues and eigenvectors of a symmetric matrix

PRECISE Function

"precise" finds a machine precision value as selected by the input argument: (1) the smallest positive floating point value, (2) the smallest relative floating point spacing, (3) the largest relative floating point spacing

PRECOND Subroutine

"precond" solves a simplified version of the Newton equations Ms = r, and uses the result to precondition linear conjugate gradient iterations on the full Newton equations in "tnsolve"

PRESSURE Subroutine

"pressure" uses the internal virial to find the pressure in a periodic box and maintains a constant desired pressure by scaling the coordinates via coupling to an external constant pressure bath

PRMKEY Subroutine

"field" parses a text string to extract keywords related to force field potential energy functional forms and constants

PROCHAIN Subroutine

"prochain" builds up the internal coordinates for an amino acid sequence from the phi, psi, omega and chi values

PROJCT Subroutine

PROMO Subroutine

"promo" writes a short message containing information about the TINKER version number and the copyright notice

PROPERTY Function

"property" takes two input snapshot frames and computes the value of the property for which the correlation function is being accumulated

PROPYZE Subroutine

"propyze" finds and prints the total charge, dipole moment components, radius of gyration and moments of inertia

PROSIDE Subroutine

"proside" builds the side chain for a single amino acid residue in terms of internal coordinates

PROTEIN Program

"protein" builds the internal and Cartesian coordinates of a polypeptide from amino acid sequence and torsional angle values for the peptide backbone and side chains

PRTARC Subroutine

"prtarc" writes out a set of Cartesian coordinates for all active atoms in the TINKER XYZ archive format

PRTCAR Subroutine

"prtcar" writes out a set of Cartesian coordinates for all active atoms in the Accelerys InsightII .car format

PRTDYN Subroutine

"prtdyn" writes out the information needed to restart a molecular dynamics trajectory to an external disk file

PRTERR Subroutine

"prterr" writes out a set of coordinates to a disk file prior to aborting on a serious error

PRTINT Subroutine

"prtint" writes out a set of Z-matrix internal coordinates to an external disk file

PRTMOL2 Program

"prtmol2" writes out a set of coordinates in Sybyl MOL2 format to an external disk file

PRTPDB Subroutine

"prtpdb" writes out a set of Protein Data Bank coordinates to an external disk file

PRTPRM Subroutine

"prtprm" writes out a formatted listing of the default set of potential energy parameters for a force field

PRTSEQ Subroutine

"prtseq" writes out a biopolymer sequence to an external disk file with 15 residues per line and distinct chains separated by blank lines

PRTXMOL Subroutine

"prtxmol" writes out a set of Cartesian coordinates for all active atoms in a simple, generic XYZ format originally used by the XMOL program

PRTXYZ Subroutine

"prtxyz" writes out a set of Cartesian coordinates to an external disk file

PSS Program

"pss" implements the potential smoothing plus search method for global optimization in Cartesian coordinate space with local searches performed in Cartesian or torsional space

PSS1 Function

"pss1" is a service routine that computes the energy and gradient during PSS global optimization in Cartesian coordinate space

PSS2 Subroutine

"pss2" is a service routine that computes the sparse matrix Hessian elements during PSS global optimization in Cartesian coordinate space

PSSRGD1 Function

"pssrgd1" is a service routine that computes the energy and gradient during PSS global optimization over rigid bodies

PSSRIGID Program

"pssrigid" implements the potential smoothing plus search method for global optimization for a set of rigid bodies

PSSROT Program

"pssrot" implements the potential smoothing plus search method for global optimization in torsional space

PSSROT1 Function

"pssrot1" is a service routine that computes the energy and gradient during PSS global optimization in torsional space

PSSWRITE Subroutine

PTINCY Function

PZEXTR Subroutine

"pzextr" is a polynomial extrapolation routine used during Bulirsch-Stoer integration of ordinary differential equations

QRFACT Subroutine

"qrfact" performs Householder transformations with column pivoting (optional) to compute a QR factorization of the m by n matrix a; the routine determines an orthogonal matrix q, a permutation matrix p, and an upper trapezoidal matrix r with diagonal elements of nonincreasing magnitude, such that a*p = q*r; the Householder transformation for column k, k = 1,2,...,min(m,n), is of the form

QRSOLVE Subroutine

"qrsolve" solves a*x=b and d*x=0 in the least squares sense; normally used in combination with routine "qrfact" to solve least squares problems

QUATFIT Subroutine

"quatfit" uses a quaternion-based method to achieve the best fit superposition of two sets of coordinates

RADIAL Program

"radial" finds the radial distribution function for a specified pair of atom types via analysis of a set of coordinate frames

RANDOM Function

"random" generates a random number on [0,1] via a long period generator due to L'Ecuyer with Bays-Durham shuffle

RANVEC Subroutine

"ranvec" generates a unit vector in 3-dimensional space with uniformly distributed random orientation

RATTLE Subroutine

"rattle" implements the first portion of the rattle algorithm by correcting atomic positions and half-step velocities to maintain interatomic distance and absolute spatial constraints

RATTLE2 Subroutine

"rattle2" implements the second portion of the rattle algorithm by correcting the full-step velocities in order to maintain interatomic distance constraints

READBLK Subroutine

"readblk" reads in a set of snapshot frames and transfers the values to internal arrays for use in the computation of time correlation functions

READDYN Subroutine

"readdyn" get the positions, velocities and accelerations for a molecular dynamics restart from an external disk file

READINT Subroutine

"readint" gets a set of Z-matrix internal coordinates from an external file

READMOL2 Subroutine

"readmol2" gets a set of Sybyl MOL2 coordinates from an external disk file

READPDB Subroutine

"readpdb" gets a set of Protein Data Bank coordinates from an external disk file

READPRM Subroutine

"readprm" processes the potential energy parameter file in order to define the default force field parameters

READSEQ Subroutine

"readseq" gets a biopolymer sequence containing one or more separate chains from an external file; all lines containing sequence must begin with the starting sequence number, the actual sequence is read from subsequent nonblank characters

READXYZ Subroutine

"readxyz" gets a set of Cartesian coordinates from an external disk file

REFINE Subroutine

"refine" performs minimization of the atomic coordinates of an initial crude embedded distance geometry structure versus the bound, chirality, planarity and torsional error functions

RELEASEMONITOR Subroutine

REPLICA Subroutine

"replica" decides between images and replicates for generation of periodic boundary conditions, and sets the cell replicate list if the replicates method is to be used

RFINDEX Subroutine

"rfindex" finds indices for each multipole site for use in computing reaction field energetics

RGDSRCH Subroutine

RGDSTEP Subroutine

"rgdstep" performs a single molecular dynamics time step for a rigid body calculation

RIBOSOME Subroutine

"ribosome" translates a polypeptide structure in Protein Data Bank format to a Cartesian coordinate file and sequence file

RIGIDXYZ Subroutine

"rigidxyz" computes Cartesian coordinates for a rigid body group via rotation and translation of reference coordinates

RINGS Subroutine

"rings" searches the structure for small rings and stores their constituent atoms

RMSERROR Subroutine

"rmserror" computes the maximum absolute deviation and the rms deviation from the distance bounds, and the number and rms value of the distance restraint violations

RMSFIT Function

"rmsfit" computes the rms fit of two coordinate sets

ROTANG Function

ROTCHECK Function

"rotcheck" tests a specified candidate rotatable bond for the disallowed case where inactive atoms are found on both sides of the candidate bond

ROTEULER Subroutine

"roteuler" computes a set of Euler angle values consistent with an input rotation matrix

ROTLIST Subroutine

"rotlist" generates the minimum list of all the atoms lying to one side of a pair of directly bonded atoms; optionally finds the minimal list by choosing the side with fewer atoms

ROTMAT Subroutine

"rotmat" finds the rotation matrix that converts from the local coordinate system to the global frame at a multipole site

ROTPOLE Subroutine

"rotpole" constructs the set of atomic multipoles in the global frame by applying the correct rotation matrix for each site

ROTRGD Subroutine

"rotrgd" finds the rotation matrix for a rigid body due to a single step of dynamics

ROTSITE Subroutine

"rotsite" computes the atomic multipoles at a specified site in the global coordinate frame by applying a rotation matrix

SADDLE Program

"saddle" finds a transition state between two conformational minima using a combination of ideas from the synchronous transit (Halgren-Lipscomb) and quadratic path (Bell-Crighton) methods

SADDLE1 Function

"saddle1" is a service routine that computes the energy and gradient for transition state optimization

SADDLES Subroutine

"saddles" constructs circles, convex edges and saddle faces

SCAN Prog