MCCCS Towhee (Charmm22 Extra Parameters for Fluoroalkanes)



    This section covers some extra parameters for use in combination with the CHARMM22 force field as it is implemented into the towhee_ff_Charmm22fe file in the ForceFields directory. This file is only likely to be useful in combination with the standard CHARMM22 forcefield. Charmm22x is a Lennard-Jones (12-6) force field and typically uses the Lorentz-Berthelot mixing rules. The parameters in this force field were developed for fluoroethanes. However, to extend the force field's capability to handle other fluorohydrocarbons, missing bond, angle and torsion terms are assumed to be equal to the similar ones reported in the reference. These new additions are the sole responsibility of Marcus G. Martin.


References for Charmm22fe Charmm22fe in Towhee
    The official force field name for Charmm222fe in Towhee is 'Charmm22' as the name has to be the same in order to get the molecule assembler to consider these parameters when building a molecule. Here is the list of atom names for use in the towhee_input file, along with a brief description. Please note that the capitalization and spacing pattern is important and must be followed exactly as listed here.
    • 'CF1' : carbon in monofluoroethane
    • 'CF2' : carbon in difluoroethane
    • 'CF3' : carbon in trifluoroethane
    • 'HF1' : hydrogen in monofluoroethanes
    • 'HF2' : hydrogen in difluoroethanes
    • 'F1' : fluorine in monofluoroethane
    • 'F2' : fluorine in difluoroethane
    • 'F3' fluorine in trifluoroethane
Coulombic interactions
    In the original paper following partial charges were reported
  • 'CF1' -0.06
  • 'CF2' 0.24
  • 'CF3' 0.38
  • 'HF1' 0.11
  • 'HF2' 0.10
  • 'F1' -0.22
  • 'F2' -0.19
  • 'F3' -0.15


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