forked from lijiext/lammps
93 lines
3.3 KiB
HTML
93 lines
3.3 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 bond/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 bond/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>bond/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>dist</I> or <I>eng</I>
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<PRE> <I>dist</I> = tabulate bond distances
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<I>eng</I> = tablutate bond energies
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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 bond/local eng
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compute 1 all bond/local dist eng
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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 bond
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interactions. The number of datums generated, aggregated across all
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processors, equals the number of bonds in the system, modified
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by the group parameter as explained below.
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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 owned on a processor and their bonds. A bond will only be
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included if both atoms in the bond are in the specified compute group.
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Any bonds that have been broken (see the <A HREF = "bond_style.html">bond_style</A>
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command) by setting their bond type to 0 are not included. Bonds that
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have been turned off (see the <A HREF = "fix_shake.html">fix shake</A> or
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<A HREF = "delete_bonds.html">delete_bonds</A> commands) by setting their bond type
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negative are written into the file, but their energy will be 0.0.
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</P>
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<P>Note that as atoms migrate from processor to processor, there will be
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no consistent ordering of the entries within the local vector or array
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from one timestep to the next. The only consistency that is
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guaranteed is that the ordering on a particular timestep will be the
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same for local vectors or arrays generated by other compute commands.
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For example, bond output from the <A HREF = "compute_property_local.html">compute
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property/local</A> command can be combined
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with data from this command and output by the <A HREF = "dump.html">dump local</A>
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command in a consistent way.
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</P>
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<P>Here is an example of how to do this:
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</P>
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<PRE>compute 1 all property/local batom1 batom2 btype
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compute 2 all bond/local dist eng
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dump 1 all local 1000 tmp.dump index c_1[1] c_1[2] c_1[3] c_2[1] c_2[2]
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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 bonds. If a single keyword is specified, a
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local vector is produced. If two or more keywords are specified, a
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local array is produced where the number of columns = the number of
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keywords. The vector or array can be accessed by any command that
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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 output for <I>dist</I> will be in distance <A HREF = "units.html">units</A>. The
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output for <I>eng</I> will be in energy <A HREF = "units.html">units</A>.
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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>, <A HREF = "compute_property_local.html">compute
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property/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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