2007-05-15 00:14:29 +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 coord/atom command
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</H3>
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<P><B>Syntax:</B>
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</P>
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2012-08-08 23:17:00 +08:00
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<PRE>compute ID group-ID coord/atom cutoff type1 type2 ...
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2007-05-15 00:14:29 +08:00
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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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2007-05-15 00:21:52 +08:00
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<LI>coord/atom = style name of this compute command
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2012-08-08 23:17:00 +08:00
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<LI>cutoff = distance within which to count coordination neighbors (distance units)
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<LI>typeN = atom type for Nth coordination count (see asterisk form below)
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2007-05-15 00:14:29 +08:00
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</UL>
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<P><B>Examples:</B>
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</P>
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2012-08-08 23:17:00 +08:00
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<PRE>compute 1 all coord/atom 2.0
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compute 1 all coord/atom 6.0 1 2
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compute 1 all coord/atom 6.0 2*4 5*8 *
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2007-05-15 00:14:29 +08:00
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</PRE>
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<P><B>Description:</B>
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</P>
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2012-08-08 23:17:00 +08:00
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<P>Define a computation that calculates one or more coordination numbers
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for each atom in a group.
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2007-05-15 00:14:29 +08:00
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</P>
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2012-08-08 23:17:00 +08:00
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<P>A coordination number is defined as the number of neighbor atoms with
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specified atom type(s) that are within the specified cutoff distance
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from the central atom. Atoms not in the group are included in a
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coordination number of atoms in the group.
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</P>
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<P>The <I>typeN</I> keywords allow you to specify which atom types contribute
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to each coordination number. One coordination number is computed for
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each of the <I>typeN</I> keywords listed. If no <I>typeN</I> keywords are
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listed, a single coordination number is calculated, which includes
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atoms of all types (same as the "*" format, see below).
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2007-11-20 23:37:16 +08:00
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</P>
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2012-08-08 23:17:00 +08:00
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<P>The <I>typeN</I> keywords can be specified in one of two ways. An explicit
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numeric value can be used, as in the 2nd example above. Or a
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wild-card asterisk can be used to specify a range of atom types. This
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takes the form "*" or "*n" or "n*" or "m*n". If N = the number of
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atom types, then an asterisk with no numeric values means all types
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from 1 to N. A leading asterisk means all types from 1 to n
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(inclusive). A trailing asterisk means all types from n to N
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(inclusive). A middle asterisk means all types from m to n
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(inclusive).
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</P>
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<P>The value of all coordination numbers will be 0.0 for atoms not in the
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specified compute group.
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2007-05-15 00:14:29 +08:00
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</P>
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<P>The neighbor list needed to compute this quantity is constructed each
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time the calculation is performed (i.e. each time a snapshot of atoms
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is dumped). Thus it can be inefficient to compute/dump this quantity
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2012-08-08 23:17:00 +08:00
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too frequently.
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2007-05-15 00:14:29 +08:00
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</P>
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2008-01-04 08:56:10 +08:00
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<P><B>Output info:</B>
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</P>
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2012-08-08 23:17:00 +08:00
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<P>If single <I>type1</I> keyword is specified (or if none are specified),
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this compute calculates a per-atom vector. If multiple <I>typeN</I>
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keywords are specified, this compute calculates a per-atom array, with
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N columns. These values can be accessed by any command that uses
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per-atom values from a compute as input. See <A HREF = "Section_howto.html#howto_15">Section_howto
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15</A> for an overview of LAMMPS output
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options.
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2008-01-04 08:56:10 +08:00
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</P>
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2012-08-08 23:17:00 +08:00
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<P>The per-atom vector or array values will be a number >= 0.0, as
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explained above.
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2010-01-24 07:20:05 +08:00
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</P>
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2007-05-15 00:14:29 +08:00
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<P><B>Restrictions:</B> none
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</P>
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2011-03-09 06:23:59 +08:00
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<P><B>Related commands:</B>
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</P>
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<P><A HREF = "compute_cluster_atom.html">compute cluster/atom</A>
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2007-05-15 00:14:29 +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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