forked from lijiext/lammps
62 lines
2.1 KiB
HTML
62 lines
2.1 KiB
HTML
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<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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</CENTER>
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<HR>
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<H3>compute displace/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 displace/atom fix-ID
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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>displace/atom = style name of this compute command
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<LI>fix-ID = ID of a fix of style <A HREF = "fix_coord_original.html">coord/original</A>
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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 displace/atom myCoords
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Define a computation that calculates the current displacement of each
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atom in the group from its original coordinates, including all effects
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due to atoms passing thru periodic boundaries. The original
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coordinates are stored by a <A HREF = "fix_coord_original.html">fix
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coord/original</A> command, whose ID must be
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specified with this compute. They are the coordinates at the time the
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fix command was issued. The displacement can be output directly via
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the <A HREF = "dump.html">dump custom</A> command. It could also be used to
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calculate a diffusion coefficient for a group of atoms, as is done by
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the <A HREF = "fix_msd.html">fix msd</A> command.
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</P>
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<P>The value of the displacement will be 0.0 for atoms not in the
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specified compute group. Note that the fix defines its own group and
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stores (0.0,0.0,0.0) for the original coordinates of any atom not in
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the fix group.
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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 vector of length 4 for each atom, which can
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be accessed by indices 1-4 by any command that uses per-atom computes
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as input. See <A HREF = "Section_howto.html#4_15">this section</A> for an overview
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of LAMMPS output options. The first 3 components of the vector are
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the x,y,z displacements. The 4th component is the total displacement,
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i.e. sqrt(dx*dx + dy*dy + dz*dz).
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</P>
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<P><B>Restrictions:</B> none
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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 = "dump.html">dump custom</A>, <A HREF = "fix_msd.html">fix msd</A>
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</P>
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<P><B>Default:</B> none
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</P>
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</HTML>
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