LAMMPS WWW Site - LAMMPS Documentation - LAMMPS Commands

### pair_style morse command

### pair_style morse/opt command

Syntax:

    pair_style morse cutoff

- cutoff = global cutoff for Morse interactions (distance units)

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

Description:

Style morse computes pairwise interactions with the formula

Rc is the cutoff.

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

- D0 (energy units)
- alpha (1/distance units)
- r0 (distance units)
- cutoff (distance units)

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).

Mixing, shift, table, tail correction, restart, rRESPA info:

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

All of these pair styles support the pair_modify shift option for the energy of the pair interaction.

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

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

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

These pair styles can only be used via the pair keyword of the run_style respa command. They do not support the inner, middle, outer keywords.

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 for more info.

Related commands:

pair_coeff

Default: none