forked from lijiext/lammps
83 lines
2.6 KiB
HTML
83 lines
2.6 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 basal/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 basal/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>basal/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 basal/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 hexagonal close-packed "c"
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lattice vector for each atom in the group. It does this by
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calculating the normal unit vector to the basal plane for each atom.
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The results enable efficient identification and characterization of
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twins and grains in hexagonal close-packed structures.
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</P>
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<P>The output of the compute is thus the 3 components of a unit vector
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associdate with each atom. The components are set to 0.0 for
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atoms not in the group.
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</P>
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<P>Details of the calculation are given in <A HREF = "#Barrett">(Barrett)</A>.
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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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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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<P>An example input script that uses this compute is provided
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in examples/USER/misc/basal.
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</P>
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<P><B>Output info:</B>
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</P>
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<P>This compute calculates a per-atom array with 3 columns, which can be
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accessed by indices 1-3 by any command that uses per-atom values from
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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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</P>
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<P>The per-atom vector values are unitless since the 3 columns represent
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components of a unit vector.
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</P>
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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-MISC package. It is only enabled if
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LAMMPS was built with that package. See the <A HREF = "Section_start.html#start_3">Making
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LAMMPS</A> section for more info.
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</P>
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<P>The output of this compute will be meaningless unless the atoms are on
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(or near) hcp lattice sites, since the calculation assumes a
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well-defined basal plane.
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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>, <A HREF = "compute_ackland_atom.html">compute
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ackland/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 = "Barrett"></A>
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<P><B>(Barrett)</B> Barrett, Tschopp, El Kadiri, Scripta Mat. 66, p.666 (2012).
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</P>
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</HTML>
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