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doc/compute_pair.txt
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@ -10,15 +10,17 @@ compute pair command :h3
[Syntax:]
compute ID group-ID pair pstyle :pre
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 :ul
pstyle = style name of a pair style that calculates additional values
evalue = {epair} or {evdwl} or {evoul} 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:]
@ -28,32 +30,44 @@ 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 that produces additional
values. If a "hybrid pair style"_pair_hybrid.html is used, then
{pstyle} should be the name of a sub-style.
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.
All pair styles tally a potential energy, which is accessed by the
"compute pe"_compute_pe.html and "compute
pe/atom"_compute_pe_atom.html commands. Some pair styles tally one or
more additional values, such as a breakdown of the total pair
potential energy into sub-categories. See the doc page for
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} + {evoul}.
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.
The compute pair command lets you access this data as a global vector
of values and then use other "output options"_Section_howto.html#4_15
that work with "compute commands"_compute.html to see or use the
values.
[Output info:]
This compute calculates a global vector of length >= 1, as determined
by the pair style. These values can be used by any command that uses
global vector values from a compute as input. See "this
section"_Section_howto.html#4_15 for an overview of LAMMPS output
options.
This compute calculates a global scalar which is {epair} or {evdwl} or
{evoul}. 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#4_15
for an overview of LAMMPS output options.
The vector values calculated by this compute are "extensive". They
are in whatever units the pair style produces.
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
@ -61,4 +75,6 @@ are in whatever units the pair style produces.
"compute pe"_compute_pe.html
[Default:] none
[Default:]
The default for {evalue} is {epair}.