"Higher level section"_Howto.html - "LAMMPS WWW Site"_lws - "LAMMPS
Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Commands_all.html)

:line

CHARMM, AMBER, COMPASS, and DREIDING force fields :h3

A force field has 2 parts: the formulas that define it and the
coefficients used for a particular system.  Here we only discuss
formulas implemented in LAMMPS that correspond to formulas commonly
used in the CHARMM, AMBER, COMPASS, and DREIDING force fields.  Setting
coefficients is done either from special sections in an input data file
via the "read_data"_read_data.html command or in the input script with
commands like "pair_coeff"_pair_coeff.html or
"bond_coeff"_bond_coeff.html and so on.  See the "Tools"_Tools.html doc
page for additional tools that can use CHARMM, AMBER, or Materials
Studio generated files to assign force field coefficients and convert
their output into LAMMPS input.

See "(MacKerell)"_#howto-MacKerell for a description of the CHARMM force
field.  See "(Cornell)"_#howto-Cornell for a description of the AMBER
force field.  See "(Sun)"_#howto-Sun for a description of the COMPASS
force field.

:link(charmm,http://www.scripps.edu/brooks)
:link(amber,http://amber.scripps.edu)

The interaction styles listed below compute force field formulas that
are consistent with common options in CHARMM or AMBER.  See each
command's documentation for the formula it computes.

"bond_style"_bond_harmonic.html harmonic
"angle_style"_angle_charmm.html charmm
"dihedral_style"_dihedral_charmm.html charmmfsh
"dihedral_style"_dihedral_charmm.html charmm
"pair_style"_pair_charmm.html lj/charmmfsw/coul/charmmfsh
"pair_style"_pair_charmm.html lj/charmmfsw/coul/long
"pair_style"_pair_charmm.html lj/charmm/coul/charmm
"pair_style"_pair_charmm.html lj/charmm/coul/charmm/implicit
"pair_style"_pair_charmm.html lj/charmm/coul/long :ul

"special_bonds"_special_bonds.html charmm
"special_bonds"_special_bonds.html amber :ul

NOTE: For CHARMM, newer {charmmfsw} or {charmmfsh} styles were released
in March 2017.  We recommend they be used instead of the older {charmm}
styles.  See discussion of the differences on the "pair
charmm"_pair_charmm.html and "dihedral charmm"_dihedral_charmm.html doc
pages.

COMPASS is a general force field for atomistic simulation of common
organic molecules, inorganic small molecules, and polymers which was
developed using ab initio and empirical parameterization techniques.
See the "Tools"_Tools.html doc page for the msi2lmp tool for creating
LAMMPS template input and data files from BIOVIA's Materials Studio
files.  Please note that the msi2lmp tool is very old and largely
unmaintained, so it does not support all features of Materials Studio
provided force field files, especially additions during the last decade.
You should watch the output carefully and compare results, where
possible.  See "(Sun)"_#howto-Sun for a description of the COMPASS force
field.

These interaction styles listed below compute force field formulas that
are consistent with the COMPASS force field.  See each command's
documentation for the formula it computes.

"bond_style"_bond_class2.html class2
"angle_style"_angle_class2.html class2
"dihedral_style"_dihedral_class2.html class2
"improper_style"_improper_class2.html class2 :ul

"pair_style"_pair_class2.html lj/class2
"pair_style"_pair_class2.html lj/class2/coul/cut
"pair_style"_pair_class2.html lj/class2/coul/long :ul

"special_bonds"_special_bonds.html lj/coul 0 0 1 :ul

DREIDING is a generic force field developed by the "Goddard
group"_http://www.wag.caltech.edu at Caltech and is useful for
predicting structures and dynamics of organic, biological and main-group
inorganic molecules. The philosophy in DREIDING is to use general force
constants and geometry parameters based on simple hybridization
considerations, rather than individual force constants and geometric
parameters that depend on the particular combinations of atoms involved
in the bond, angle, or torsion terms. DREIDING has an "explicit hydrogen
bond term"_pair_hbond_dreiding.html to describe interactions involving a
hydrogen atom on very electronegative atoms (N, O, F).

See "(Mayo)"_#howto-Mayo for a description of the DREIDING force field

The interaction styles listed below compute force field formulas that
are consistent with the DREIDING force field.  See each command's
documentation for the formula it computes.

"bond_style"_bond_harmonic.html harmonic
"bond_style"_bond_morse.html morse :ul

"angle_style"_angle_harmonic.html harmonic
"angle_style"_angle_cosine.html cosine
"angle_style"_angle_cosine_periodic.html cosine/periodic :ul

"dihedral_style"_dihedral_charmm.html charmm
"improper_style"_improper_umbrella.html umbrella :ul

"pair_style"_pair_buck.html buck
"pair_style"_pair_buck.html buck/coul/cut
"pair_style"_pair_buck.html buck/coul/long
"pair_style"_pair_lj.html lj/cut
"pair_style"_pair_lj.html lj/cut/coul/cut
"pair_style"_pair_lj.html lj/cut/coul/long :ul

"pair_style"_pair_hbond_dreiding.html hbond/dreiding/lj
"pair_style"_pair_hbond_dreiding.html hbond/dreiding/morse :ul

"special_bonds"_special_bonds.html dreiding :ul

:line

:link(howto-MacKerell)
[(MacKerell)] MacKerell, Bashford, Bellott, Dunbrack, Evanseck, Field,
Fischer, Gao, Guo, Ha, et al, J Phys Chem, 102, 3586 (1998).

:link(howto-Cornell)
[(Cornell)] Cornell, Cieplak, Bayly, Gould, Merz, Ferguson,
Spellmeyer, Fox, Caldwell, Kollman, JACS 117, 5179-5197 (1995).

:link(howto-Sun)
[(Sun)] Sun, J. Phys. Chem. B, 102, 7338-7364 (1998).

:link(howto-Mayo)
[(Mayo)] Mayo, Olfason, Goddard III, J Phys Chem, 94, 8897-8909
(1990).
