<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 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 <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>1 = UNKNOWN <LI>2 = BCC <LI>3 = FCC <LI>4 = HCP <LI>5 = 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>Restrictions:</B> none </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>