2007-02-10 05:40:32 +08:00
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<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
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<HR>
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<H3>compute command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>compute ID group-ID style args
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</PRE>
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<UL><LI>ID = user-assigned name for the computation
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<LI>group-ID = ID of the group of atoms to perform the computation on
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<LI>style = one of a list of possible style names (see below)
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<LI>args = arguments used by a particular style
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>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
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Create a computation that will be performed on a group of atoms.
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</P>
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2007-09-28 07:25:52 +08:00
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<P>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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2007-02-10 05:40:32 +08:00
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</P>
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2007-09-28 07:25:52 +08:00
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<P>The results of global computes can be output via the <A HREF = "thermo_style.html">thermo_style
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custom</A> or <A HREF = "fix_ave_time.html">fix ave/time</A> command.
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Or the values can be referenced in a <A HREF = "variable.html">variable equal</A>
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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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</P>
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<P>The results of per-atom computes can be output via the <A HREF = "dump.html">dump
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custom</A> command or the <A HREF = "fix_ave_spatial.html">fix
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ave/spatial</A> command. Or the per-atom values can
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be time-averaged via the <A HREF = "fix_ave_atom.html">fix ave/atom</A> command and
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then output via the <A HREF = "dump.html">dump custom</A> or <A HREF = "fix_ave_spatial.html">fix
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2007-11-20 23:37:16 +08:00
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ave/spatial</A> commands. Note that the value of
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per-atom computes will be 0.0 for atoms not in the specified compute
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group.
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2007-09-28 07:25:52 +08:00
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</P>
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2007-10-10 02:24:42 +08:00
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<P>See this <A HREF = "Section_howto.html#4_15">howto section</A> for a summary of
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various LAMMPS output options.
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</P>
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2007-11-02 00:46:50 +08:00
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<P>LAMMPS creates its own global computes for thermodynamic output.
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Three computes are always created, named "thermo_temp",
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"thermo_pressure", and"thermo_pe", as if these commands had been
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invoked in the input script:
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2007-06-20 20:56:17 +08:00
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</P>
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<PRE>compute thermo_temp all temp
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2007-11-02 00:46:50 +08:00
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compute thermo_pressure all pressure thermo_temp
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compute thermo_pe all pe
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2007-06-20 20:56:17 +08:00
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</PRE>
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<P>Additional computes are created if the thermo style requires it. See
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the documentation for the <A HREF = "thermo_style.html">thermo_style</A> command.
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</P>
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<P>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 <A HREF = "dump.html">dump custom</A> and specific
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<A HREF = "fix.html">fix</A> commands.
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2007-02-10 05:40:32 +08:00
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</P>
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<P>In all these cases, the default computes can be replaced by computes
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2007-09-28 07:25:52 +08:00
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defined by the user in the input script, as described by the
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<A HREF = "thermo_modify.html">thermo_modify</A>, <A HREF = "fix_modify.html">fix modify</A>, and
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<A HREF = "dump.html">dump</A> commands.
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2007-06-20 20:56:17 +08:00
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</P>
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<P>Properties of either a default of user-defined compute can be modified
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via the <A HREF = "compute_modify.html">compute_modify</A> command.
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2007-02-10 05:40:32 +08:00
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</P>
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2007-06-20 20:56:17 +08:00
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<P>Computes can be deleted with the <A HREF = "uncompute.html">uncompute</A> command.
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2007-02-10 05:40:32 +08:00
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</P>
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2007-06-20 20:56:17 +08:00
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<P>Code for new computes can be added to LAMMPS (see <A HREF = "Section_modify.html">this
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section</A> of the manaul) and the results of their
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calculations accessed in the various ways described above.
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2007-02-10 05:40:32 +08:00
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</P>
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<P>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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</P>
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2007-09-28 07:25:52 +08:00
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<UL><LI><A HREF = "compute_attribute_atom.html">attribute/atom</A> - attribute (x,v,f,etc) of each atom
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<LI><A HREF = "compute_centro_atom.html">centro/atom</A> - centro-symmetry parameter for each atom
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2007-06-20 21:09:50 +08:00
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<LI><A HREF = "compute_coord_atom.html">coord/atom</A> - coordination number for each atom
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2007-07-03 23:30:03 +08:00
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<LI><A HREF = "compute_ebond_atom.html">ebond/atom</A> - bond energy for each atom
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2007-02-10 05:40:32 +08:00
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<LI><A HREF = "compute_epair_atom.html">epair/atom</A> - pairwise energy for each atom
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<LI><A HREF = "compute_ke_atom.html">ke/atom</A> - kinetic energy for each atom
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2007-11-02 00:46:50 +08:00
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<LI><A HREF = "compute_pe.html">pe</A> - potential energy
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2007-02-10 05:40:32 +08:00
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<LI><A HREF = "compute_pressure.html">pressure</A> - total pressure and pressure tensor
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<LI><A HREF = "compute_rotate_dipole.html">rotate/dipole</A> - rotational energy of dipolar atoms
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<LI><A HREF = "compute_rotate_gran.html">rotate/gran</A> - rotational energy of granular atoms
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<LI><A HREF = "compute_stress_atom.html">stress/atom</A> - stress tensor for each atom
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2007-10-27 04:42:35 +08:00
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<LI><A HREF = "compute_sum.html">sum</A> - sum per-atom quantities to a global value
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<LI><A HREF = "compute_sum_atom.html">sum/atom</A> - sum per-atom quantities to per-atom values
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2007-02-10 05:40:32 +08:00
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<LI><A HREF = "compute_temp.html">temp</A> - temperature of group of atoms
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2007-06-20 21:09:50 +08:00
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<LI><A HREF = "compute_temp_asphere.html">temp/asphere</A> - temperature of aspherical particles
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<LI><A HREF = "compute_temp_deform.html">temp/deform</A> - temperature excluding box deformation velocity
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<LI><A HREF = "compute_temp_dipole.html">temp/dipole</A> - temperature of point dipolar particles
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2007-02-10 05:40:32 +08:00
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<LI><A HREF = "compute_temp_partial.html">temp/partial</A> - temperature excluding one or more dimensions of velocity
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2007-06-20 21:09:50 +08:00
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<LI><A HREF = "compute_temp_ramp.html">temp/ramp</A> - temperature excluding ramped velocity component
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2007-02-21 08:18:01 +08:00
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<LI><A HREF = "compute_temp_region.html">temp/region</A> - temperature of a region of atoms
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2007-04-20 07:25:27 +08:00
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<LI><A HREF = "compute_variable.html">variable</A> - calculate a scalar value from a variable
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2007-02-21 08:18:01 +08:00
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<LI><A HREF = "compute_variable_atom.html">variable/atom</A> - calculate a formula for each atom
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2007-02-10 05:40:32 +08:00
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</UL>
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2007-10-03 06:56:45 +08:00
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<P>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 <A HREF = "Section_commands.html#3_5">this
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page</A>.
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</P>
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2007-02-10 05:40:32 +08:00
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<P><B>Restrictions:</B> none
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</P>
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<P><B>Related commands:</B>
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</P>
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2007-10-27 04:42:35 +08:00
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<P><A HREF = "uncompute.html">uncompute</A>, <A HREF = "compute_modify.html">compute_modify</A>, <A HREF = "fix_ave_atom.html">fix
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ave/atom</A>, <A HREF = "fix_ave_spatial.html">fix ave/spatial</A>,
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<A HREF = "fix_ave_time.html">fix ave/time</A>
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2007-02-10 05:40:32 +08:00
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</P>
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<P><B>Default:</B> none
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</P>
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</HTML>
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