forked from lijiext/lammps
104 lines
3.7 KiB
Plaintext
104 lines
3.7 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 pe command :h3
|
|
compute pe/cuda command :h3
|
|
|
|
[Syntax:]
|
|
|
|
compute ID group-ID pe keyword ... :pre
|
|
|
|
ID, group-ID are documented in "compute"_compute.html command
|
|
pe = style name of this compute command
|
|
zero or more keywords may be appended
|
|
keyword = {pair} or {bond} or {angle} or {dihedral} or {improper} or {kspace} :ul
|
|
|
|
[Examples:]
|
|
|
|
compute 1 all pe
|
|
compute molPE all pe bond angle dihedral improper :pre
|
|
|
|
[Description:]
|
|
|
|
Define a computation that calculates the potential energy of the
|
|
entire system of atoms. The specified group must be "all". See the
|
|
"compute pe/atom"_compute_pe_atom.html command if you want per-atom
|
|
energies. These per-atom values could be summed for a group of atoms
|
|
via the "compute reduce"_compute_reduce.html command.
|
|
|
|
The energy is calculated by the various pair, bond, etc potentials
|
|
defined for the simulation. If no extra keywords are listed, then the
|
|
potential energy is the sum of pair, bond, angle, dihedral, improper,
|
|
and kspace (long-range) energy. If any extra keywords are listed,
|
|
then only those components are summed to compute the potential energy.
|
|
|
|
The Kspace contribution requires 1 extra FFT each timestep the energy
|
|
is calculated, if using the PPPM solver via the "kspace_style
|
|
pppm"_kspace_style.html command. Thus it can increase the cost of the
|
|
PPPM calculation if it is needed on a large fraction of the simulation
|
|
timesteps.
|
|
|
|
Various fixes can contribute to the total potential energy of the
|
|
system. See the doc pages for "individual fixes"_fix.html for
|
|
details. The {thermo} option of the
|
|
"compute_modify"_compute_modify.html command determines whether these
|
|
contributions are added into the computed potential energy. If no
|
|
keywords are specified the default is {yes}. If any keywords are
|
|
specified, the default is {no}.
|
|
|
|
A compute of this style with the ID of "thermo_pe" is created when
|
|
LAMMPS starts up, as if this command were in the input script:
|
|
|
|
compute thermo_pe all pe :pre
|
|
|
|
See the "thermo_style" command for more details.
|
|
|
|
:line
|
|
|
|
Styles with a {cuda}, {gpu}, {intel}, {kk}, {omp}, or {opt} suffix are
|
|
functionally the same as the corresponding style without the suffix.
|
|
They have been optimized to run faster, depending on your available
|
|
hardware, as discussed in "Section_accelerate"_Section_accelerate.html
|
|
of the manual. The accelerated styles take the same arguments and
|
|
should produce the same results, except for round-off and precision
|
|
issues.
|
|
|
|
These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
|
|
KOKKOS, USER-OMP and OPT packages, respectively. They are only
|
|
enabled if LAMMPS was built with those packages. See the "Making
|
|
LAMMPS"_Section_start.html#start_3 section for more info.
|
|
|
|
You can specify the accelerated styles explicitly in your input script
|
|
by including their suffix, or you can use the "-suffix command-line
|
|
switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
|
|
use the "suffix"_suffix.html command in your input script.
|
|
|
|
See "Section_accelerate"_Section_accelerate.html of the manual for
|
|
more instructions on how to use the accelerated styles effectively.
|
|
|
|
:line
|
|
|
|
[Output info:]
|
|
|
|
This compute calculates a global scalar (the potential energy). This
|
|
value can be used by any command that uses a global scalar value from
|
|
a compute as input. See "Section_howto
|
|
15"_Section_howto.html#howto_15 for an overview of LAMMPS output
|
|
options.
|
|
|
|
The scalar value calculated by this compute is "extensive". The
|
|
scalar value will be in energy "units"_units.html.
|
|
|
|
[Restrictions:] none
|
|
|
|
[Related commands:]
|
|
|
|
"compute pe/atom"_compute_pe_atom.html
|
|
|
|
[Default:] none
|