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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>
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<H3>fix gyration command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>fix ID group-ID gyration N file
</PRE>
<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
<LI>gyration = style name of this fix command
<LI>N = compute radius-of-gyration every this many timesteps
<LI>file = filename to write gyration info to
</UL>
<P><B>Examples:</B>
</P>
<PRE>fix 1 all gyration 100 molecule.out
</PRE>
<P><B>Description:</B>
</P>
<P>Compute the radius-of-gyration of the group of atoms every N steps,
including all effects due to atoms passing thru periodic boundaries.
Write the results to the specified file.
</P>
<P>Rg is a measure of the size of the group of atoms, and is computed by
this formula
</P>
<CENTER><IMG SRC = "Eqs/fix_gyration.jpg">
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<P>where M is the total mass of the group and Rcm is the center-of-mass
position of the group.
</P>
<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
</P>
<P>No information about this fix is written to <A HREF = "restart.html">binary restart
files</A>. None of the <A HREF = "fix_modify.html">fix_modify</A> options
are relevant to this fix. No global scalar or vector or per-atom
quantities are stored by this fix for access by various <A HREF = "Section_howto.html#4_15">output
commands</A>. No parameter of this fix can be
used with the <I>start/stop</I> keywords of the <A HREF = "run.html">run</A> command.
This fix is not invoked during <A HREF = "minimize.html">energy minimization</A>.
</P>
<P><B>Restrictions:</B> none
</P>
<P><B>Related commands:</B> none
</P>
<P><B>Default:</B> none
</P>
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