lammps/doc/pair_morse.txt

"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

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

:line

pair_style morse command :h3
pair_style morse/opt command :h3

[Syntax:]

pair_style morse cutoff :pre

cutoff = global cutoff for Morse interactions (distance units) :ul

[Examples:]

pair_style morse 2.5
pair_style morse/opt 2.5
pair_coeff * * 100.0 2.0 1.5
pair_coeff 1 1 100.0 2.0 1.5 3.0 :pre

[Description:]

Style {morse} computes pairwise interactions with the formula

:c,image(Eqs/pair_morse.jpg)

Rc is the cutoff.

The following coefficients must be defined for each pair of atoms
types via the "pair_coeff"_pair_coeff.html command as in the examples
above, or in the data file or restart files read by the
"read_data"_read_data.html or "read_restart"_read_restart.html
commands:

D0 (energy units)
alpha (1/distance units)
r0 (distance units)
cutoff (distance units) :ul

The last coefficient is optional.  If not specified, the global morse
cutoff is used.

Style {morse/opt} is an optimized version of style {morse} that should
give identical answers.  Depending on system size and the processor
you are running on, it may be 5-25% faster (for the pairwise portion
of the run time).

:line

[Mixing, shift, table, tail correction, per-atom energy/stress, and
restart info]:

None of the Morse pair styles support mixing.  Thus, coefficients for
all I,J pairs must be specified explicitly.

All of the Morse pair styles support the
"pair_modify"_pair_modify.html shift option for the energy of the pair
interaction.

The "pair_modify"_pair_modify.html table options is not relevant for
the Morse pair styles.

None of the Morse pair styles support the
"pair_modify"_pair_modify.html tail option for adding long-range tail
corrections to energy and pressure.

All of the Morse pair styles can calculate per-atom energy and
stress, as used by the "compute epair/atom"_compute_epair_atom.html,
"compute stress/atom"_compute_stress_atom.html, and "dump
custom"_dump.html commands.

All of the Morse pair styles write their information to "binary
restart files"_restart.html, so pair_style and pair_coeff commands do
not need to be specified in an input script that reads a restart file.

:line

[Restrictions:]

The {morse/opt} style is part of the "opt" package.  It is only
enabled if LAMMPS was built with that package.  See the "Making
LAMMPS"_Section_start.html#2_3 section for more info.

[Related commands:]

"pair_coeff"_pair_coeff.html

[Default:] none