forked from lijiext/lammps
64 lines
1.9 KiB
HTML
64 lines
1.9 KiB
HTML
<HTML>
|
|
<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>
|
|
</CENTER>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<HR>
|
|
|
|
<H3>compute centro/atom command
|
|
</H3>
|
|
<P><B>Syntax:</B>
|
|
</P>
|
|
<PRE>compute ID group-ID centro/atom
|
|
</PRE>
|
|
<UL><LI>ID, group-ID are documented in <A HREF = "compute.html">compute</A> command
|
|
<LI>centro/atom = style name of this compute command
|
|
</UL>
|
|
<P><B>Examples:</B>
|
|
</P>
|
|
<PRE>compute 1 all centro/atom
|
|
</PRE>
|
|
<P><B>Description:</B>
|
|
</P>
|
|
<P>Define a computation that calculates the centro-symmetry parameter for
|
|
each atom in a group. This can be output via the <A HREF = "dump.html">dump
|
|
custom</A> command. In solid state systems the centro-symmetry
|
|
parameter is a useful measure of the local lattice disorder around an
|
|
atom and can be used to characterize whether the atom is part of a
|
|
perfect lattice, a local defect (e.g. a dislocation or stacking
|
|
fault), or at a surface.
|
|
</P>
|
|
<P>This parameter is computed using the following formula from
|
|
<A HREF = "#Kelchner">(Kelchner)</A>
|
|
</P>
|
|
<CENTER><IMG SRC = "Eqs/centro_symmetry.jpg">
|
|
</CENTER>
|
|
<P>where the 12 nearest neighbors are found and Ri and Ri+6 are the
|
|
vectors from the central atom to the opposite pair of nearest
|
|
neighbors. Atoms not in the group are included in the 12 neighbors
|
|
used in this calculation.
|
|
</P>
|
|
<P>The neighbor list needed to compute this quantity is constructed each
|
|
time the calculation is performed (i.e. each time a snapshot of atoms
|
|
is dumped). Thus it can be inefficient to compute/dump this quantity
|
|
too frequently or to have multiple compute/dump commands, each of a
|
|
<I>centro/atom</I> style.
|
|
</P>
|
|
<P><B>Restrictions:</B> none
|
|
</P>
|
|
<P><B>Related commands:</B> none
|
|
</P>
|
|
<P><B>Default:</B> none
|
|
</P>
|
|
<HR>
|
|
|
|
<A NAME = "Kelchner"></A>
|
|
|
|
<P><B>(Kelchner)</B> Kelchner, Plimpton, Hamilton, Phys Rev B, 58, 11085 (1998).
|
|
</P>
|
|
</HTML>
|