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### pair_style born command

### pair_style born/coul/long command

Syntax:

    pair_style style args

- style = born or born/coul/long
- args = list of arguments for a particular style

      born args = cutoff
        cutoff = global cutoff for non-Coulombic interactions (distance units)
      born/coul/long args = cutoff (cutoff2)
        cutoff = global cutoff for non-Coulombic (and Coulombic if only 1 arg) (distance units)
        cutoff2 = global cutoff for Coulombic (optional) (distance units)

Examples:

    pair_style born 10.0
    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

    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:

The born style computes the Born-Mayer-Huggins or Tosi/Fumi 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 Rc is the cutoff.

The born/coul/long style adds a Coulombic term as described for the lj/cut pair styles. 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.

If one cutoff is specified for the born/coulk/long style, 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 these potentials are related to the Buckingham potential.

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 second coefficient, rho, must be greater than zero.

The last coefficient is optional. If not specified, the global A,C,D cutoff specified in the pair_style command is used.

For buck/coul/long no Coulombic cutoff can 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:

These pair styles do not support mixing. Thus, coefficients for all I,J pairs must be specified explicitly.

These styles support the pair_modify shift option for the energy of the exp(), 1/r^6, and 1/r^8 portion of the pair interaction.

The born/coul/long pair style does not support the pair_modify table option since a tabulation capability has not yet been added to this potential.

These styles support the pair_modify tail option for adding long-range tail corrections to energy and pressure.

Thess styles writes thei 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 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 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).