MCCCS Towhee (Charmm27 Extra Parameters)



    This section covers some extra parameters for use in combination with the CHARMM27 force field as it is implemented into the towhee_ff_Charmm27x file in the ForceFields directory. This file is only likely to be useful in combination with the standard CHARMM27 forcefield. Charmm27x is a Lennard-Jones (12-6) force field and typically uses the Lorentz-Berthelot mixing rules. These values are not actually from the CHARMM27 forcefield and are the sole responsibility of Marcus G. Martin.


References for Charmm27x
    These are some additional parameters created by Marcus G. Martin for use with the actual CHARMM27 forcefield. Some of these parameters were published in the following paper.
  • Martin and Biddy 2005
Typos and comments for Charmm27x
  • This file is an example of the suggested method for users to add additional parameters to existing forcefields. By placing all of the additional parameters into a separate file this makes it easy to both keep track of your changes for eventual publication, and to upgrade to new code versions without worrying about overwriting your new parameters.
  • In order to use these additional parameters with the CHARMM27 forcefield you need to include both the towhee_ff_Charmm27 and towhee_ff_Charmm27x forcefield files in towhee_input. Label the molecules with the 'Charmm27' forcefield as normal and Towhee will search through the forcefield files in the order specified and take the first complete match.
  • The following parameters were published in Martin and Biddy 2005.
    • CT3-CC-CT3: used for acetone and taken from the CHARMM27 CT3-CT2-CT2 parameters.
Charmm27x in Towhee
    The official force field name for Charmm27x in Towhee is 'Charmm27' as the name has to be the same in order to get the molecule assembler to consider these parameters when building a molecule. There are no additional nonbonded types in this forcefield. See the original CHARMM27 forcefield for the valid atom types.


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Send comments to: Marcus G. Martin
Last updated: May 03, 2006