Syntax:
pair_style style args
lj/class2 args = cutoff cutoff = global cutoff for class 2 interactions (distance units) lj/class2/coul/cut args = cutoff (cutoff2) cutoff = global cutoff for class 2 (and Coulombic if only 1 arg) (distance units) cutoff2 = global cutoff for Coulombic (optional) (distance units) lj/class2/coul/long args = cutoff (cutoff2) cutoff = global cutoff for class 2 (and Coulombic if only 1 arg) (distance units) cutoff2 = global cutoff for Coulombic (optional) (distance units)
Examples:
pair_style lj/class2 10.0 pair_coeff * * 100.0 2.5 pair_coeff 1 2* 100.0 2.5 9.0
pair_style lj/class2/coul/cut 10.0 pair_style lj/class2/coul/cut 10.0 8.0 pair_coeff * * 100.0 3.0 pair_coeff 1 1 100.0 3.5 9.0 pair_coeff 1 1 100.0 3.5 9.0 9.0
pair_style lj/class2/coul/long 10.0 pair_style lj/class2/coul/long 10.0 8.0 pair_coeff * * 100.0 3.0 pair_coeff 1 1 100.0 3.5 9.0
Description:
The lj/class2 styles compute a 6/9 Lennard-Jones potential given by
Rc is the cutoff.
The lj/class2/coul/cut and lj/class2/coul/long styles add a Coulombic term as described for the lj/cut pair styles.
See (Sun) for a description of the COMPASS class2 force field.
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 class 2 and Coulombic cutoffs are used. If only one cutoff is specified, it is used as the cutoff for both class 2 and Coulombic interactions for this type pair. If both coefficients are specified, they are used as the class 2 and Coulombic cutoffs for this type pair. You cannot specify 2 cutoffs for style lj/class2, since it has no Coulombic terms.
For lj/class2/coul/long only the class 2 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:
These styles are part of the "class2" package. They are 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 lj/class2/coul/long style. See the "Additional build tips" section of the Making LAMMPS documentation pages for workarounds on this issue.
Related commands:
Default: none
(Sun) Sun, J Phys Chem B 102, 7338-7364 (1998).