forked from lijiext/lammps
100 lines
3.7 KiB
HTML
100 lines
3.7 KiB
HTML
<HTML>
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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 body/local 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 body/local input1 input2 ...
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</PRE>
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<UL><LI>ID, group-ID are documented in <A HREF = "compute.html">compute</A> command
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<LI>body/local = style name of this compute command
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<LI>one or more keywords may be appended
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<LI>keyword = <I>type</I> or <I>integer</I>
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<PRE> <I>type</I> = atom type of the body particle
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<I>integer</I> = 1,2,3,etc = index of fields defined by body style
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</PRE>
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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 body/local type 1 2 3
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compute 1 all body/local 3 6
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Define a computation that calculates properties of individual body
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sub-particles. The number of datums generated, aggregated across all
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processors, equals the number of body sub-particles plus the number of
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non-body particles in the system, modified by the group parameter as
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explained below. See <A HREF = "Section_howto.html#howto_14">Section_howto 14</A>
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of the manual and the <A HREF = "body.html">body</A> doc page for more details on
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using body particles.
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</P>
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<P>The local data stored by this command is generated by looping over all
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the atoms. An atom will only be included if it is in the group. If
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the atom is a body particle, then its N sub-particles will be looped
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over, and it will contribute N datums to the count of datums. If it
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is not a body particle, it will contribute 1 datum.
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</P>
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<P>For both body particles and non-body particles, the <I>type</I> keyword
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will store the type of the atom.
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</P>
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<P>The <I>integer</I> keywords mean different things for body and non-body
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particles. If the atom is not a body particle, only its <I>x</I>, <I>y</I>, <I>z</I>
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coordinates can be referenced, using the <I>integer</I> keywords 1,2,3.
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Note that this means that if you want to access more fields than this
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for body particles, then you cannot include non-body particles in the
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group.
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</P>
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<P>For a body particle, the <I>integer</I> keywords refer to fields calculated
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by the body style for each sub-particle. The body style, as specified
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by the <A HREF = "atom_style.html">atom_style body</A>, determines how many fields
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exist and what they are. See the <A HREF = "body.html">body</A> doc page for
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details of the different styles.
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</P>
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<P>Here is an example of how to output body information using the <A HREF = "dump.html">dump
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local</A> command with this compute. If fields 1,2,3 for the
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body sub-particles are x,y,z coordinates, then the dump file will be
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formatted similar to the output of a <A HREF = "dump.html">dump atom or custom</A>
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command.
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</P>
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<PRE>compute 1 all body/local type 1 2 3
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dump 1 all local 1000 tmp.dump index c_1[1] c_1[2] c_1[3] c_1[4]
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</PRE>
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<P><B>Output info:</B>
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</P>
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<P>This compute calculates a local vector or local array depending on the
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number of keywords. The length of the vector or number of rows in the
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array is the number of datums as described above. If a single keyword
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is specified, a local vector is produced. If two or more keywords are
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specified, a local array is produced where the number of columns = the
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number of keywords. The vector or array can be accessed by any
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command that uses local values from a compute as input. See <A HREF = "Section_howto.html#howto_15">this
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section</A> for an overview of LAMMPS output
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options.
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</P>
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<P>The <A HREF = "units.html">units</A> for output values depend on the body style.
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</P>
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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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<P><A HREF = "dump.html">dump local</A>
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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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