forked from lijiext/lammps
57 lines
1.6 KiB
Plaintext
57 lines
1.6 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 variable/atom command :h3
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[Syntax:]
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compute ID group-ID variable/atom name :pre
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ID, group-ID are documented in "compute"_compute.html command
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variable/atom = style name of this compute command
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name = variable name to invoke for each atom :ul
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[Examples:]
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compute 1 flow variable/atom myVar :pre
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[Description:]
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Define a computation that calculates a formula for each atom in the
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group. The per-atom quantities can be output via the "dump
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custom"_dump.html command or spatially averaged via the "fix
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ave/spatial"_fix_ave_spatial.html command.
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The formula is defined by the "variable atom"_variable.html command.
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A variable of style {atom} can access properties of the system, such
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as volume or temperature, and also reference individual atom
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attributes, such as its coordinates or velocity.
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For example, these 3 commands would compute the xy kinectic energy of
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atoms in the flow group and include the values in dumped snapshots of
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the system.
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variable xy atom mult(0.5,add(mult(vx\[\],vx\[\]),mult(vy\[\],vy\[\])))
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compute ke flow variable/atom xy
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dump 1 flow custom 1000 dump.flow tag type x y z c_ke :pre
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If the dump line were replaced by
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fix 1 flow ave/spatial 100 1000 z lower 2.0 ke.profile compute ke :pre
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then the xy kinetic energy values would be averaged by z layer and the
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layer averages written periodically to the file ke.profile.
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[Restrictions:] none
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[Related commands:]
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"dump custom"_dump.html, "fix ave/spatial"_fix_ave_spatial.html
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[Default:] none
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