forked from lijiext/lammps
68 lines
2.4 KiB
Plaintext
68 lines
2.4 KiB
Plaintext
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"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,Section_commands.html#comm)
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:line
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compute attribute/atom command :h3
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[Syntax:]
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compute ID group-ID attribute/atom style :pre
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ID, group-ID are documented in "compute"_compute.html command
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attribute/atom = style name of this compute command
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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
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[Examples:]
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compute 1 all attribute/atom vy
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compute mine all attribute/atom xyz :pre
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[Description:]
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Define a computation that calculates (or simply stores) one or more
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attributes for each atom in a group. This is useful for input to the
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"fix ave/spatial"_fix_ave_spatial.html command to do spatial averaging
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by layers or to the "fix ave/atom"_fix_ave_atom.html command to
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perform time-averaging of per-atom quantities. The attribute values
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can also be output directly by the "dump custom"_dump.html command,
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but it has keywords that output these quantities without the need to
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define an additional compute.
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The styles {x}, {y}, {z}, {xu}, {yu}, {zu}, {vx}, {vy}, {vz}, {fx},
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{fy}, and {fz} each store a single scalar value per atom.
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The {x}, {y}, {z} keywords store atom coordinate in the appropriate
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distance "units"_units.html (Angstroms, sigma, etc) and will always be
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inside (or slightly outside) the simulation box. Use {xu}, {yu}, {zu}
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if you want the coordinates "unwrapped" by the image flags for each
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atom. Unwrapped means that if the atom has passed thru a periodic
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boundary one or more times, the value is printed for what the
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coordinate would be if it had not been wrapped back into the periodic
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box. Note that using {xu}, {yu}, {zu} means that the coordinate
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values may be far outside the simulation box.
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Note that if you want to compute the time-averaged position of an atom
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coordinate that could pass thru a periodic boundary (e.g. via the "fix
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ave/atom"_fix_ave_atom.html command), you probably want to use {xu}
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instead of {x}.
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The styles {xyz}, {v}, and {f} each store a vector of 3 quantities per
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atom.
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Note that the various commands that reference this compute use a
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different syntax for accessing scalar versus vector values, e.g. c_ID
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versus c_ID[2].
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[Restrictions:] none
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[Related commands:]
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"fix ave/atom"_fix_ave_atom.html, "fix
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ave/spatial"_fix_ave_spatial.html, "dump custom"_dump.html
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[Default:] none
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