Syntax:
pair_style style args
buck args = cutoff cutoff = global cutoff for Buckingham interactions (distance units) buck/coul/cut args = cutoff (cutoff2) cutoff = global cutoff for Buckingham (and Coulombic if only 1 arg) (distance units) cutoff2 = global cutoff for Coulombic (optional) (distance units) buck/coul/long args = cutoff (cutoff2) cutoff = global cutoff for Buckingham (and Coulombic if only 1 arg) (distance units) cutoff2 = global cutoff for Coulombic (optional) (distance units)
Examples:
pair_style buck 2.5 pair_coeff * * 100.0 1.5 200.0 pair_coeff * * 100.0 1.5 200.0 3.0
pair_style buck/coul/cut 10.0 pair_style buck/coul/cut 10.0 8.0 pair_coeff * * 100.0 1.5 200.0 pair_coeff 1 1 100.0 1.5 200.0 9.0 pair_coeff 1 1 100.0 1.5 200.0 9.0 8.0
pair_style buck/coul/long 10.0 pair_style buck/coul/long 10.0 8.0 pair_coeff * * 100.0 1.5 200.0 pair_coeff 1 1 100.0 1.5 200.0 9.0
Description:
The buck style computes a Buckingham potential (exp/6 instead of Lennard-Jones 12/6) given by
Rc is the cutoff.
The buck/coul/cut and buck/coul/long styles add a Coulombic term as described for the lj/cut pair styles.
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:
The latter 2 coefficients are optional. If not specified, the global LJ and Coulombic cutoffs are used. If only one cutoff is specified, it is used as the cutoff for both LJ and Coulombic interactions for this type pair. If both coefficients are specified, they are used as the LJ and Coulombic cutoffs for this type pair. You cannot specify 2 cutoffs for style buck, since it has no Coulombic terms.
For buck/coul/long only the LJ 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.
Restrictions:
The buck potentials do not support the pair_modify mix option. Coefficients for all i,j pairs must be specified explicitly.
The buck/coul/long style is part of the "kspace" package. It is only enabled if LAMMPS was built with that package. See the Making LAMMPS section for more info.
On some 64-bit machines, compiling with -O3 appears to break the Coulombic tabling option used by the buck/coul/long style. See the "Additional build tips" section of the Making LAMMPS documentation pages for workarounds on this issue.
Related commands:
Default: none