forked from lijiext/lammps
86 lines
2.9 KiB
Plaintext
86 lines
2.9 KiB
Plaintext
"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 force/tally command :h3
|
|
compute heat/flux/tally command :h3
|
|
compute pe/tally command :h3
|
|
compute stress/tally command :h3
|
|
|
|
[Syntax:]
|
|
|
|
compute ID group-ID style group2-ID :pre
|
|
|
|
ID, group-ID are documented in "compute"_compute.html command
|
|
style = {force/tally} or {pe/tally} or {stress/tally}
|
|
group2-ID = group ID of second (or same) group :ul
|
|
|
|
[Examples:]
|
|
|
|
compute 1 lower force/tally upper
|
|
compute 1 left pe/tally right
|
|
compute 1 lower stress/tally lower :pre
|
|
|
|
[Description:]
|
|
|
|
Define a computation that calculates properties between two groups of
|
|
atoms by accumulating them from pairwise non-bonded computations. The
|
|
two groups can be the same. This is similar to "compute
|
|
group/group"_compute_group_group.html only that the data is
|
|
accumulated directly during the non-bonded force computation. The
|
|
computes {force/tally}, {pe/tally}, {stress/tally}, and
|
|
{heat/flux/tally} are primarily provided as example how to program
|
|
additional, more sophisticated computes using the tally mechanism.
|
|
|
|
:line
|
|
|
|
The pairwise contributions are computing via a callback that the
|
|
compute registers with the non-bonded pairwise force computation.
|
|
This limits the use to systems that have no bonds, no Kspace, and no
|
|
manybody interactions. On the other hand, the computation does not
|
|
have to compute forces or energies a second time and thus can be much
|
|
more efficient. The callback mechanism allows to write more complex
|
|
pairwise property computations.
|
|
|
|
:line
|
|
|
|
[Output info:]
|
|
|
|
Compute {pe/tally} calculates a global scalar (the energy) and a per
|
|
atom scalar (the contributions of the single atom to the global
|
|
scalar). Compute {force/tally} calculates a global scalar (the force
|
|
magnitude) and a per atom 3-element vector (force contribution from
|
|
each atom). Compute {stress/tally} calculates a global scalar
|
|
(average of the diagonal elements of the stress tensor) and a per atom
|
|
vector (the 6 elements of stress tensor contributions from the
|
|
individual atom).
|
|
|
|
Both the scalar and vector values calculated by this compute are
|
|
"extensive".
|
|
|
|
[Restrictions:]
|
|
|
|
This compute is part of the USER-TALLY package. It is only enabled
|
|
if LAMMPS was built with that package. See the "Making
|
|
LAMMPS"_Section_start.html#start_3 section for more info.
|
|
|
|
Not all pair styles can be evaluated in a pairwise mode as required by
|
|
this compute. For example, 3-body and other many-body potentials,
|
|
such as "Tersoff"_pair_tersoff.html and
|
|
"Stillinger-Weber"_pair_sw.html cannot be used. "EAM"_pair_eam.html
|
|
potentials only include the pair potential portion of the EAM
|
|
interaction when used by this compute, not the embedding term. Also
|
|
bonded or Kspace interactions do not contribute to this compute.
|
|
|
|
[Related commands:]
|
|
|
|
{compute group/group}_compute_group_group.html, {compute
|
|
heat/flux}_compute_heat_flux.html
|
|
|
|
[Default:] none
|
|
|