
                ###############################################
                Tinker Implementation of the MMFF94 Force Field
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     Developed by Nicolas Staelens, University of Namur, 11/2005 to 04/2007
     Further adapted for Tinker by Jay W. Ponder, Washington Univ, 02/2009

     The Info.pdf file in this directory contains comments from Nicolas
     Staelens regarding his original implementation of MMFF in Tinker.

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                               Usage Instructions
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     The mmff.prm parameter file may be used just as you would any other
     Tinker parameter file. The only caveat is that all MMFF "bond type=1"
     bonds must be listed in the Tinker keyfile via a MMFF-PIBOND keyword.
     This keyword takes as arguments the atom numbers of atoms in type=1
     bonds. Up to ten bonded atom pairs (ie, 20 atom numbers) are listed
     following the MMFF-PIBOND keyword. Multiple MMFF-PIBOND keywords can
     be present. The MMFF bond type=1 is used for conjugated bonds that are
     "single" bonds in reasonable resonance forms, but could otherwise be
     double bonds in other structures. For example, the middle C-C bond in
     1,3-butadiene has an MMFF bond type of 1.

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                             Validation Test Cases
                             #####################

     The "validation" subdirectory contains a nearly complete set of files
     for the MMFF Validation Suite deposited by Tom Halgren with the CCL.
     Some 740 structures are provided, and the only structures missing from
     the Halgren set are those with ionic heteroaromatic rings. Tinker key
     files with MMFF-PIBOND keywords are provided for the 292 molecules
     requiring explicit listing of bonds with MMFF bond type of 1. Output
     files are provided to allow verification of energy components.

