This section covers the Potter et al. 1997 (Potter1997) force field as it is implemented into
the towhee_ff_Potter1997 file in the ForceFields directory. This force field was
designed to reproduce the vapour-liquid equilibria for three different fluoromethane molecules.
Note that this is a Lennard-Jones force field that uses the 'LB plus manual' mixing rules, and therefore
you will need to explicitly set some cross terms in towhee_input in order to use this force field as
the authors intended.
Any discrepencies (especially typos) from the published values are the sole responsibility
of Marcus G. Martin, and I welcome feedback on how this implementation compares
with other programs.
References for Potter et al. 1997
This forcefield is described in a single paper.
Typos and comments for Potter et al. 1997
Potter et al. 1997 in Towhee
- Please note that you need to explicitly set the cross terms for H and F in towhee_input in order to properly
reproduce their work. The cross terms for the H-F interactions should have a sigma of 2.3 Angstrom and an epsilon
of 22.36 Kelvin. See the Potter_CF2H2 example for
more information about how to set these cross terms.
The official force field name for Potter et al. 1997 in Towhee is 'Potter1997'. Here is the list
of atom names for use in the towhee_input file, along with a brief description. I created these names in
order to distinguish between the different hydrogen and fluorine parmeters that are used depending upon the
extent of methane fluorination.
Please note that the capitalization and spacing pattern is important
and must be followed exactly as listed here.
- 'C' : Carbon in any of the fluoromethanes
- 'F(2)' : Fluorine in CH2F2
- 'F(3)' : Fluorine in CHF3
- 'F(4)' : Fluorine in CF4
- 'H(2)' : Hydrogen in CH2F2
- 'H(1)' : Hydrogen in CHF3
This force field uses point charges and has been set up to assign the point charges using the bond increment method.
The charges for bmim are assigned according to Table 1 of
Potter et al. 1997.
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