"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 attribute/atom command :h3

[Syntax:]

compute ID group-ID attribute/atom style :pre

ID, group-ID are documented in "compute"_compute.html command
attribute/atom = style name of this compute command
style = {x} or {y} or {z} or {xu} or {yu} or {zu} or {vx} or {vy} or {vz} or {fx} or {fy} or {fz} or {xyz} or {v} or {f} :ul

[Examples:]

compute 1 all attribute/atom vy
compute mine all attribute/atom xyz :pre

[Description:]

Define a computation that calculates (or simply stores) one or more
attributes for each atom in a group.  This is useful for input to the
"fix ave/spatial"_fix_ave_spatial.html command to do spatial averaging
by layers or to the "fix ave/atom"_fix_ave_atom.html command to
perform time-averaging of per-atom quantities.  The attribute values
can also be output directly by the "dump custom"_dump.html command,
but it has keywords that output these quantities without the need to
define an additional compute.

The value of the attribute will be 0.0 for atoms not in the specified
compute group.

The styles {x}, {y}, {z}, {xu}, {yu}, {zu}, {vx}, {vy}, {vz}, {fx},
{fy}, and {fz} each store a single scalar value per atom.

The {x}, {y}, {z} keywords store atom coordinate in the appropriate
distance "units"_units.html (Angstroms, sigma, etc) and will always be
inside (or slightly outside) the simulation box.  Use {xu}, {yu}, {zu}
if you want the coordinates "unwrapped" by the image flags for each
atom.  Unwrapped means that if the atom has passed thru a periodic
boundary one or more times, the value is printed for what the
coordinate would be if it had not been wrapped back into the periodic
box.  Note that using {xu}, {yu}, {zu} means that the coordinate
values may be far outside the simulation box.

Note that if you want to compute the time-averaged position of an atom
coordinate that could pass thru a periodic boundary (e.g. via the "fix
ave/atom"_fix_ave_atom.html command), you probably want to use {xu}
instead of {x}.

The styles {xyz}, {v}, and {f} each store a vector of 3 quantities per
atom.

Note that the various commands that reference this compute use a
different syntax for accessing scalar versus vector values, e.g. c_ID
versus c_ID\[2\].

[Restrictions:] none

[Related commands:]

"fix ave/atom"_fix_ave_atom.html, "fix
ave/spatial"_fix_ave_spatial.html, "dump custom"_dump.html

[Default:] none
