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### pair_style born/coul/long command

Syntax:

    pair_style born/coul/long cutoff (cutoff2)

- cutoff = global cutoff for LJ (and Coulombic if only 1 arg) (distance units)
- cutoff2 = global cutoff for Coulombic (optional) (distance units)

Examples:

    pair_style born/coul/long 10.0
    pair_style born/coul/long 10.0 8.0
    pair_coeff * * 6.08 0.317 2.340 24.18 11.51
    pair_coeff 1 1 6.08 0.317 2.340 24.18 11.51

Description:

This pair style compute the Born-Mayer-Huggins potential described in (Fumi and Tosi), given by

where sigma is an interaction-dependent length parameter, rho is an ionic-pair dependent length parameter, and the last term represents the usual Coulombic pairwise interaction between atoms I and J. In the Coulombic term, k is an energy-conversion constant, Qi and Qj are the charges on the 2 atoms, and epsilon is the dielectric constant which can be set by the dielectric command.

If one cutoff is specified in the pair_style command, it is used for both the A,C,D and Coulombic terms. If two cutoffs are specified, the first is used as the cutoff for the A,C,D terms, and the second is the cutoff for the Coulombic term.

Note that this potential is identical to the Buckingham potential when sigma = D = 0.

An additional damping factor is applied to the Coulombic term so it can be used in conjunction with the kspace_style command and its ewald or pppm option. The Coulombic cutoff specified for this style means that pairwise interactions within this distance are computed directly; interactions outside that distance are computed in reciprocal space.

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, or by mixing as described below:

- A (energy units)
- rho (distance units)
- sigma (distance units)
- C (energy units * distance units^6)
- D (energy units * distance units^8)
- cutoff (distance units)

The last coefficient is optional. If not specified, the global A,C,D cutoff specified in the pair_style command is used. Only the A,C,D cutoff can be specified since a Coulombic cutoff cannot be specified for an individual I,J type pair. All type pairs use the same global Coulombic cutoff specified in the pair_style command.

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

This style does not support mixing. Thus, coefficients for all I,J pairs must be specified explicitly.

This style supports the pair_modify shift option for the energy of the exp(), 1/r^6, and 1/r^8 portion of the pair interaction.

This style does not support the pair_modify table option since a tabulation capability has not yet been added to this potential.

This style does not support the pair_modify tail option for adding long-range tail corrections to energy and pressure.

This style writes its 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.

This style only supports the pair keyword of run_style respa. See the run_style command for details.

Restrictions:

The born/coul/long style is part of the "kspace" package. It is only enabled if LAMMPS was built with that package (which it is by default). See the Making LAMMPS section for more info.

Related commands:

pair_coeff, pair_style buck

Default: none

Fumi and Tosi, J Phys Chem Solids, 25, 31 (1964), Fumi and Tosi, J Phys Chem Solids, 25, 45 (1964).