2015-07-30 22:38:28 +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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</CENTER>
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2009-12-22 08:34:36 +08:00
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2015-07-30 22:38:28 +08:00
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<HR>
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2009-12-22 08:34:36 +08:00
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2015-07-30 22:38:28 +08:00
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<H3>fix store/force 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 store/force
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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>store/force = 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 1 all store/force
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Store the forces on atoms in the group at the point during each
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2010-06-04 08:14:14 +08:00
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timestep when the fix is invoked, as described below. This is useful
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for storing forces before constraints or other boundary conditions are
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computed which modify the forces, so that unmodified forces can be
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2015-07-30 22:38:28 +08:00
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<A HREF = "dump.html">written to a dump file</A> or accessed by other <A HREF = "Section_howto.html#howto_15">output
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commands</A> that use per-atom quantities.
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</P>
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<P>This fix is invoked at the point in the velocity-Verlet timestepping
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immediately after <A HREF = "pair_style.html">pair</A>, <A HREF = "bond_style.html">bond</A>,
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<A HREF = "angle_style.html">angle</A>, <A HREF = "dihedral_style.html">dihedral</A>,
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<A HREF = "improper_style.html">improper</A>, and <A HREF = "kspace_style.html">long-range</A>
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2009-12-22 08:34:36 +08:00
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forces have been calculated. It is the point in the timestep when
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various fixes that compute constraint forces are calculated and
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potentially modify the force on each atom. Examples of such fixes are
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2015-07-30 22:38:28 +08:00
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<A HREF = "fix_shake.html">fix shake</A>, <A HREF = "fix_wall.html">fix wall</A>, and <A HREF = "fix_indent.html">fix
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indent</A>.
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</P>
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<P>IMPORTANT NOTE: The order in which various fixes are applied which
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2009-12-22 09:14:57 +08:00
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operate at the same point during the timestep, is the same as the
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order they are specified in the input script. Thus normally, if you
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want to store per-atom forces due to force field interactions, before
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constraints are applied, you should list this fix first within that
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set of fixes, i.e. before other fixes that apply constraints.
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However, if you wish to include certain constraints (e.g. fix shake)
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in the stored force, then it could be specified after some fixes and
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2015-07-30 22:38:28 +08:00
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before others.
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</P>
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<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
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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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are relevant to this fix.
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</P>
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<P>This fix produces a per-atom array which can be accessed by various
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<A HREF = "Section_howto.html#howto_15">output commands</A>. The number of columns
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2011-08-26 01:01:01 +08:00
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for each atom is 3, and the columns store the x,y,z forces on each
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2015-07-30 22:38:28 +08:00
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atom. The per-atom values be accessed on any timestep.
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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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</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 = "fix_store_state.html">fix store_state</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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