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.
Typos and comments for Charmm27x
- Martin and Biddy 2005
Charmm27x in Towhee
- 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.
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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