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lammps/doc/compute_pair.txt
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"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)
:line
compute pair command :h3
[Syntax:]
compute ID group-ID pair pstyle evalue :pre
ID, group-ID are documented in "compute"_compute.html 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) :ul
[Examples:]
compute 1 all pair gauss
compute 1 all pair lj/cut/coul/cut ecoul
compute 1 all pair reax :pre
[Description:]
Define a computation that extracts additional values calculated by a
pair style, sums them across processors, 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"_pair_hybrid.html 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"_pair_hybrid.html if you want to know the portion
of the total energy contributed by one sub-style. If {evalue} is
specfied as {evdwl} or {ecoul}, then just that portion of the energy
is stored as a global scalar.
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"_pair_reax.html commmand. These values (1 or more)
are stored as a global vector by this compute. See the doc page for
"individual pair styles"_pair_style.html for info on these values.
[Output info:]
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"_Section_howto.html#howto_15 for an overview of LAMMPS output
options.
The scalar and vector values calculated by this compute are
"extensive".
The scalar value will be in energy "units"_units.html. The vector
values will typically also be in energy "units"_units.html, but
see the doc page for the pair style for details.
[Restrictions:] none
[Related commands:]
"compute pe"_compute_pe.html
[Default:]
The default for {evalue} is {epair}.
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