2006-09-22 00:22:34 +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>fix freeze command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>fix ID group-ID freeze
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</PRE>
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<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
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<LI>freeze = style name of this fix command
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>fix 2 bottom freeze
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Zero out the force and torque on a granular particle. This is useful
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2009-06-23 04:49:14 +08:00
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for preventing certain particles from moving in a simulation. The
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<A HREF = "pair_gran.html">granular pair styles</A> also detect if this fix has been
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defined and compute interactions between frozen and non-frozen
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particles appropriately, as if the frozen particle has infinite mass.
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2006-09-22 00:22:34 +08:00
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</P>
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2007-10-11 06:28:11 +08:00
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<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
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2007-06-26 08:03:39 +08:00
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</P>
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<P>No information about this fix is written to <A HREF = "restart.html">binary restart
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files</A>. None of the <A HREF = "fix_modify.html">fix_modify</A> options
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2009-06-23 04:49:14 +08:00
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are relevant to this fix.
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</P>
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<P>This fix computes a 3-vector of forces, which can be accessed by
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various <A HREF = "Section_howto.html#4_15">output commands</A>. This is the total
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force on the group of atoms before the forces on individual atoms are
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changed by the fix. The vector values calculated by this fix are
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"extensive", meaning they scale with the number of atoms in the
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simulation.
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</P>
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<P>No parameter of this fix can be used with the <I>start/stop</I> keywords of
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the <A HREF = "run.html">run</A> command. This fix is not invoked during <A HREF = "minimize.html">energy
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minimization</A>.
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2007-06-26 08:03:39 +08:00
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</P>
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2006-09-22 00:22:34 +08:00
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<P><B>Restrictions:</B>
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</P>
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2007-06-26 08:03:39 +08:00
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<P>This fix is part of the "granular" package. It is only enabled if
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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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2006-09-22 00:22:34 +08:00
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</P>
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<P>There can only be a single freeze fix defined. This is because other
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2009-06-23 04:49:14 +08:00
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the <A HREF = "pair_gran.html">granular pair styles</A> treat frozen particles
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differently and need to be able to reference a single group to which
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this fix is applied.
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2006-09-22 00:22:34 +08:00
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</P>
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<P><B>Related commands:</B> none
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</P>
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<P><A HREF = "atom_style.html">atom_style granular</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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