forked from lijiext/lammps
122 lines
5.1 KiB
Plaintext
122 lines
5.1 KiB
Plaintext
"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 command :h3
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[Syntax:]
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compute ID group-ID style args :pre
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ID = user-assigned name for the computation
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group-ID = ID of the group of atoms to perform the computation on
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style = one of a list of possible style names (see below)
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args = arguments used by a particular style :ul
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[Examples:]
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compute 1 all temp
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compute newtemp flow temp/partial 1 1 0
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compute 3 all ke/atom :pre
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[Description:]
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Create a computation that will be performed on a group of atoms.
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In LAMMPS, a "compute" is used in several ways. There are two kinds
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of computes, "global" computes that calculate one or more values for
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the entire group of atoms, and "per-atom" computes that calculate one
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or more values for each atom in the group. The latter has the word
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"atom" in its style name.
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The results of global computes can be output via the "thermo_style
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custom"_thermo_style.html or "fix ave/time"_fix_ave_time.html command.
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Or the values can be referenced in a "variable equal"_variable.html
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command. The results of computes that calculate a global temperature
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or pressure can be used by fixes that do thermostatting or
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barostatting and when atom velocities are created.
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The results of per-atom computes can be output via the "dump
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custom"_dump.html command or the "fix
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ave/spatial"_fix_ave_spatial.html command. Or the per-atom values can
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be time-averaged via the "fix ave/atom"_fix_ave_atom.html command and
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then output via the "dump custom"_dump.html or "fix
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ave/spatial"_fix_ave_spatial.html commands.
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See this "howto section"_Section_howto.html#4_15 for a summary of
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various LAMMPS output options.
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LAMMPS creates its own global computes for thermodynamic output. Two
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computes are always created, named "thermo_temp" and
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"thermo_pressure", as if these commands had been invoked:
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compute thermo_temp all temp
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compute thermo_pressure all pressure thermo_temp :pre
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Additional computes are created if the thermo style requires it. See
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the documentation for the "thermo_style"_thermo_style.html command.
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The dumping of atom snapshots and fixes that compute temperature or
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pressure also create computes as required. These are discussed in the
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documentation for the "dump custom"_dump.html and specific
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"fix"_fix.html commands.
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In all these cases, the default computes can be replaced by computes
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defined by the user in the input script, as described by the
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"thermo_modify"_thermo_modify.html, "fix modify"_fix_modify.html, and
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"dump"_dump.html commands.
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Properties of either a default of user-defined compute can be modified
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via the "compute_modify"_compute_modify.html command.
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Computes can be deleted with the "uncompute"_uncompute.html command.
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Code for new computes can be added to LAMMPS (see "this
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section"_Section_modify.html of the manaul) and the results of their
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calculations accessed in the various ways described above.
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Each compute style has its own doc page which describes its arguments
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and what it does. Here is an alphabetic list of compute styles
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defined in LAMMPS:
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"attribute/atom"_compute_attribute_atom.html - attribute (x,v,f,etc) of each atom
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"centro/atom"_compute_centro_atom.html - centro-symmetry parameter for each atom
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"coord/atom"_compute_coord_atom.html - coordination number for each atom
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"ebond/atom"_compute_ebond_atom.html - bond energy for each atom
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"epair/atom"_compute_epair_atom.html - pairwise energy for each atom
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"ke/atom"_compute_ke_atom.html - kinetic energy for each atom
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"pressure"_compute_pressure.html - total pressure and pressure tensor
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"rotate/dipole"_compute_rotate_dipole.html - rotational energy of dipolar atoms
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"rotate/gran"_compute_rotate_gran.html - rotational energy of granular atoms
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"stress/atom"_compute_stress_atom.html - stress tensor for each atom
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"sum"_compute_sum.html - sum per-atom quantities to a global value
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"sum/atom"_compute_sum_atom.html - sum per-atom quantities to per-atom values
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"temp"_compute_temp.html - temperature of group of atoms
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"temp/asphere"_compute_temp_asphere.html - temperature of aspherical particles
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"temp/deform"_compute_temp_deform.html - temperature excluding box deformation velocity
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"temp/dipole"_compute_temp_dipole.html - temperature of point dipolar particles
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"temp/partial"_compute_temp_partial.html - temperature excluding one or more dimensions of velocity
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"temp/ramp"_compute_temp_ramp.html - temperature excluding ramped velocity component
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"temp/region"_compute_temp_region.html - temperature of a region of atoms
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"variable"_compute_variable.html - calculate a scalar value from a variable
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"variable/atom"_compute_variable_atom.html - calculate a formula for each atom :ul
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There are also additional compute styles submitted by users which are
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included in the LAMMPS distribution. The list of these with links to
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the individual styles are given in the compute section of "this
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page"_Section_commands.html#3_5.
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[Restrictions:] none
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[Related commands:]
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"uncompute"_uncompute.html, "compute_modify"_compute_modify.html, "fix
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ave/atom"_fix_ave_atom.html, "fix ave/spatial"_fix_ave_spatial.html,
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"fix ave/time"_fix_ave_time.html
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[Default:] none
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