93 lines
3.4 KiB
Plaintext
93 lines
3.4 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Commands_all.html)
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:line
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compute pair command :h3
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[Syntax:]
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compute ID group-ID pair pstyle \[nstyle\] \[evalue\] :pre
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ID, group-ID are documented in "compute"_compute.html command :ulb,l
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pair = style name of this compute command :l
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pstyle = style name of a pair style that calculates additional values :l
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nsub = {n}-instance of a sub-style, if a pair style is used multiple times in a hybrid style :l
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{evalue} = {epair} or {evdwl} or {ecoul} or blank (optional) :l
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:ule
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[Examples:]
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compute 1 all pair gauss
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compute 1 all pair lj/cut/coul/cut ecoul
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compute 1 all pair tersoff 2 epair
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compute 1 all pair reax/c :pre
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[Description:]
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Define a computation that extracts additional values calculated by a
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pair style, and makes them accessible for output or further processing
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by other commands.
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NOTE: The group specified for this command is [ignored].
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The specified {pstyle} must be a pair style used in your simulation
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either by itself or as a sub-style in a "pair_style hybrid or
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hybrid/overlay"_pair_hybrid.html command. If the sub-style is
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used more than once, an additional number {nsub} has to be specified
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in order to choose which instance of the sub-style will be used by
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the compute. Not specifying the number in this case will cause the
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compute to fail.
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The {evalue} setting is optional. All
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pair styles tally a potential energy {epair} which may be broken into
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two parts: {evdwl} and {ecoul} such that {epair} = {evdwl} + {ecoul}.
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If the pair style calculates Coulombic interactions, their energy will
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be tallied in {ecoul}. Everything else (whether it is a Lennard-Jones
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style van der Waals interaction or not) is tallied in {evdwl}. If
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{evalue} is blank or specified as {epair}, then {epair} is stored
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as a global scalar by this compute. This is useful when using
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"pair_style hybrid"_pair_hybrid.html if you want to know the portion
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of the total energy contributed by one sub-style. If {evalue} is
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specified as {evdwl} or {ecoul}, then just that portion of the energy
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is stored as a global scalar.
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NOTE: The energy returned by the {evdwl} keyword does not include tail
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corrections, even if they are enabled via the
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"pair_modify"_pair_modify.html command.
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Some pair styles tally additional quantities, e.g. a breakdown of
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potential energy into 14 components is tallied by the "pair_style
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reax/c"_pair_reaxc.html command. These values (1 or more)
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are stored as a global vector by this compute. See the doc page for
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"individual pair styles"_pair_style.html for info on these values.
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[Output info:]
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This compute calculates a global scalar which is {epair} or {evdwl} or
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{ecoul}. If the pair style supports it, it also calculates a global
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vector of length >= 1, as determined by the pair style. These values
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can be used by any command that uses global scalar or vector values
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from a compute as input. See the "Howto output"_Howto_output.html doc
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page for an overview of LAMMPS output options.
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The scalar and vector values calculated by this compute are
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"extensive".
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The scalar value will be in energy "units"_units.html. The vector
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values will typically also be in energy "units"_units.html, but see
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the doc page for the pair style for details.
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[Restrictions:] none
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[Related commands:]
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"compute pe"_compute_pe.html, "compute bond"_compute_bond.html
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[Default:]
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The keyword defaults are {evalue} = {epair}, nsub = 0.
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