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lammps/tools/moltemplate/src/moltemplate_force_fields/trappe1998.lt
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trappe1998.lt
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# This file stores complete LAMMPS data for the TraPPE model of saturated
# hydrocarbon chains. In this "united-atom" model, each methyl group is
# represented by a single atom. Forces between "atoms" are taken from the
# TraPPE force-field. (J Phys Chem B, 1998, volume 102, pp.2569-2577)
TraPPE {
write_once("Data Masses") {
@atom:CH2 14.1707
@atom:CH3 15.2507
@atom:CH4 16.3307
}
write_once("Data Angles By Type") {
@angle:backbone @atom:CH? @atom:CH? @atom:CH? @bond:saturated @bond:saturated
}
write_once("Data Dihedrals By Type") {
@dihedral:backbone @atom:CH? @atom:CH? @atom:CH? @atom:CH? @bond:saturated @bond:saturated @bond:saturated
}
write_once("In Settings") {
pair_coeff @atom:CH2 @atom:CH2 lj/charmm/coul/charmm 0.091411522 3.95
pair_coeff @atom:CH3 @atom:CH3 lj/charmm/coul/charmm 0.194746286 3.75
pair_coeff @atom:CH4 @atom:CH4 lj/charmm/coul/charmm 0.294106636 3.73
bond_coeff @bond:saturated harmonic 120.0 1.54
angle_coeff @angle:backbone harmonic 62.0022 114
dihedral_coeff @dihedral:backbone opls 1.411036 -0.271016 3.145034 0.0
}
# Optional: Create a group corresponding to atoms used by the TraPPE force-
# field. (This is useful if you mix force-fields together.)
write_once("In Settings") {
group TraPPE type @atom:CH2 @atom:CH3 @atom:CH4
}
write_once("In Init") {
# -- Default styles for "TraPPE" --
units real
atom_style full
# (Hybrid force field styles were used for portability.)
bond_style hybrid harmonic
angle_style hybrid harmonic
dihedral_style hybrid opls
improper_style none
pair_style hybrid lj/charmm/coul/charmm 9.0 11.0 9.0 11.0
pair_modify mix arithmetic
special_bonds lj 0.0 0.0 0.0
}
} # class TraPPE
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