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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>
</CENTER>
<HR>
<H3>compute ackland/atom command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>compute ID group-ID ackland/atom
</PRE>
<UL><LI>ID, group-ID are documented in <A HREF = "compute.html">compute</A> command
<LI>ackland/atom = style name of this compute command
</UL>
<P><B>Examples:</B>
</P>
<PRE>compute 1 all ackland/atom
</PRE>
<P><B>Description:</B>
</P>
<P>Defines a computation that calculates the local lattice structure
according to the formulation given in <A HREF = "#Ackland">(Ackland)</A>.
</P>
<P>In contrast to the <A HREF = "compute_centro_atom.html">centro-symmetry
parameter</A> this method is stable against
temperature boost, because it is based not on the distance between
particles but the angles. Therefore statistical fluctuations are
averaged out a little more. A comparison with the Common Neighbor
Analysis metric is made in the paper.
</P>
<P>The result is a number which is mapped to the following different
lattice structures:
</P>
<UL><LI>0 = UNKNOWN
<LI>1 = BCC
<LI>2 = FCC
<LI>3 = HCP
<LI>4 = ICO
</UL>
<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
which computes this quantity.-
</P>
<P><B>Output info:</B>
</P>
<P>This compute calculates a per-atom vector, which can be accessed by
any command that uses per-atom values from a compute as input. See
<A HREF = "Section_howto.html#howto_15">Section_howto 15</A> for an overview of
LAMMPS output options.
</P>
<P><B>Restrictions:</B>
</P>
<P>This compute is part of the USER-MISC package. It is only enabled if
LAMMPS was built with that package. See the <A HREF = "Section_start.html#start_3">Making
LAMMPS</A> section for more info.
</P>
<P>The per-atom vector values will be unitless since they are the
integers defined above.
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "compute_centro_atom.html">compute centro/atom</A>
</P>
<P><B>Default:</B> none
</P>
<HR>
<A NAME = "Ackland"></A>
<P><B>(Ackland)</B> Ackland, Jones, Phys Rev B, 73, 054104 (2006).
</P>
</HTML>
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