2007-10-04 23:05:42 +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 ackland/atom 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 ackland/atom
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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>ackland/atom = style name of this compute command
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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 ackland/atom
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Defines a computation that calculates the local lattice structure
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2008-01-04 08:56:10 +08:00
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according to the formulation given in <A HREF = "#Ackland">(Ackland)</A>.
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2007-10-04 23:05:42 +08:00
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</P>
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<P>In contrast to the <A HREF = "compute_centro_atom.html">centro-symmetry
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parameter</A> this method is stable against
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temperature boost, because it is based not on the distance between
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particles but the angles. Therefore statistical fluctuations are
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averaged out a little more. A comparison with the Common Neighbor
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Analysis metric is made in the paper.
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2007-10-04 23:05:42 +08:00
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</P>
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<P>The result is a number which is mapped to the following different
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lattice structures:
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</P>
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<UL><LI>1 = UNKNOWN
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<LI>2 = BCC
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<LI>3 = FCC
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<LI>4 = HCP
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<LI>5 = ICO
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</UL>
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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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too frequently or to have multiple compute/dump commands, each of
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which computes this quantity.-
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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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<P>This compute calculates a scalar quantity for each atom, which can be
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accessed by any command that uses per-atom computes as input. See
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<A HREF = "Section_howto.html#4_15">this section</A> for an overview of LAMMPS
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output options.
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</P>
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2008-05-16 06:05:51 +08:00
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<P><B>Restrictions:</B>
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</P>
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<P>This compute is part of the "user-ackland" package. It is only
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enabled if LAMMPS was built with that package. See the <A HREF = "Section_start.html#2_3">Making
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LAMMPS</A> section for more info.
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2007-10-04 23:05:42 +08:00
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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 = "compute_centro_atom.html">compute centro/atom</A>
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</P>
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<P><B>Default:</B> none
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</P>
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<HR>
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<A NAME = "Ackland"></A>
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<P><B>(Ackland)</B> Ackland, Jones, Phys Rev B, 73, 054104 (2006).
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</P>
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</HTML>
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