"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 command :h3

[Syntax:]

compute ID group-ID style args :pre

ID = user-assigned name for the computation
group-ID = ID of the group of atoms to perform the computation on
style = one of a list of possible style names (see below)
args = arguments used by a particular style :ul

[Examples:]

compute 1 all temp
compute newtemp flow temp/partial 1 1 0
compute 3 all ke/atom :pre

[Description:]

Create a computation that will be performed on a group of atoms.

In LAMMPS, a "compute" is used in several ways.  Computes that
calculate one or more values for the entire group of atoms can output
those values via the "thermo_style custom"_thermo_style.html or "fix
ave/time"_fix_ave_time.html command.  Or the values can be referenced
in a "variable equal"_variable.html command.  Computes that calculate
a temperature or pressure are used by fixes that do thermostatting or
barostatting and when atom velocities are created.  Computes that
calculate one or more values for each atom in the group can output
those values via the "dump custom"_dump.html command or the "fix
ave/spatial"_fix_ave_spatial.html command.

LAMMPS creates its own computes for thermodynamic output and dumping
atom snapshots.  Likewise fixes that compute temperature or pressure
create their own computes.  These are discussed in the documentation
for "thermo_style"_thermo_style.html, "dump custom"_dump.html, and
specific "fix"_fix.html commands.

In all these cases, the default computes can be replaced by computes
defined in the input script, as described by the
"thermo_modify"_thermo_modify.html and "fix modify"_fix_modify.html
commands.  Code for new computes can also be added to LAMMPS (see
"this section"_Section_modify.html of the manaul) and their
calculations accessed in the various ways described above.

Properties of a compute can be modified via the
"compute_modify"_compute_modify.html command.

Compute can be deleted with the "uncompute"_uncompute.html command.

Each compute style has its own doc page which describes its arguments
and what it does.  Here is an alphabetic list of compute styles
defined in LAMMPS:

"centro/atom"_compute_centro_atom.html - centro-symmetry parameter for each atom
"epair/atom"_compute_epair_atom.html - pairwise energy for each atom
"etotal/atom"_compute_etotal_atom.html - total energy (ke + epair) for each atom
"ke/atom"_compute_ke_atom.html - kinetic energy for each atom
"pressure"_compute_pressure.html - total pressure and pressure tensor
"rotate/dipole"_compute_rotate_dipole.html - rotational energy of dipolar atoms
"rotate/gran"_compute_rotate_gran.html - rotational energy of granular atoms
"stress/atom"_compute_stress_atom.html - stress tensor for each atom
"temp"_compute_temp.html - temperature of group of atoms
"temp/partial"_compute_temp_partial.html - temperature excluding one or more dimensions of velocity
"temp/ramp"_compute_temp_ramp.html - temperature after subtracting a ramped velocity component
"temp/region"_compute_temp_region.html - temperature of a region of atoms
"variable"_compute_variable.html - calculate a scalar value from a variable
"variable/atom"_compute_variable_atom.html - calculate a formula for each atom :ul

[Restrictions:] none

[Related commands:]

"uncompute"_uncompute.html, "compute_modify"_compute_modify.html

[Default:] none