compute pair command
compute ID group-ID pair pstyle evalue
- ID, group-ID are documented in compute command
- pair = style name of this compute command
- pstyle = style name of a pair style that calculates additional values
- evalue = epair or evdwl or ecoul or blank (optional setting)
compute 1 all pair gauss compute 1 all pair lj/cut/coul/cut ecoul compute 1 all pair reax
Define a computation that extracts additional values calculated by a pair style, and makes them accessible for output or further processing by other commands. The group specified for this command is ignored.
The specified pstyle must be a pair style used in your simulation either by itself or as a sub-style in a pair_style hybrid or hybrid/overlay command.
The evalue setting is optional; it may be left off the command. All pair styles tally a potential energy epair which may be broken into two parts: evdwl and ecoul such that epair = evdwl + ecoul. If the pair style calculates Coulombic interactions, their energy will be tallied in ecoul. Everything else (whether it is a Lennard-Jones style van der Waals interaction or not) is tallied in evdwl. If evalue is specified as epair or left out, then epair is stored as a global scalar by this compute. This is useful when using pair_style hybrid if you want to know the portion of the total energy contributed by one sub-style. If evalue is specified as evdwl or ecoul, then just that portion of the energy is stored as a global scalar.
The energy returned by the evdwl keyword does not include tail corrections, even if they are enabled via the pair_modify command.
Some pair styles tally additional quantities, e.g. a breakdown of potential energy into a dozen or so components is tallied by the pair_style reax command. These values (1 or more) are stored as a global vector by this compute. See the doc page for individual pair styles for info on these values.
This compute calculates a global scalar which is epair or evdwl or ecoul. If the pair style supports it, it also calculates a global vector of length >= 1, as determined by the pair style. These values can be used by any command that uses global scalar or vector values from a compute as input. See this section for an overview of LAMMPS output options.
The scalar and vector values calculated by this compute are “extensive”.
The default for evalue is epair.