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 setforce 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 setforce fx fy fz
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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>setforce = style name of this fix command
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<LI>fx,fy,fz = force component values
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>fix freeze indenter setforce 0.0 0.0 0.0
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fix 2 edge setforce NULL 0.0 0.0
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Set each component of force on each atom in the group to the specified
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values fx,fy,fz. This erases all previously computed forces on the
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atom, though additional fixes could add new forces. This command can
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be used to freeze certain atoms in the simulation by zeroing their
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force, assuming their initial velocity zero.
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</P>
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<P>Any of the fx,fy,fz values can be specified as NULL which means do not
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alter the force component in that dimension.
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</P>
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<P>The forces due to this fix are also imposed during an energy
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minimization, invoked by the <A HREF = "minimize.html">minimize</A> command.
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</P>
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2007-03-23 00:35:32 +08:00
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<P>The total force on the group of atoms before it is reset is stored by
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the fix and its components can be accessed during thermodynamic
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2007-03-23 01:16:09 +08:00
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print-out by using f_ID[N] where ID = he fix-ID and N = 1,2,3. See
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2007-03-23 00:35:32 +08:00
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the <A HREF = "thermo_style.html">thermo_style custom</A> command for details. Note
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that the fix stores the total force on the group of atoms, but the
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printed value may be normalized by the total number of atoms in the
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simulation depending on the <A HREF = "thermo_modify.html">thermo_modify norm</A>
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option you are using.
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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> 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_addforce.html">fix addforce</A>, <A HREF = "fix_aveforce.html">fix aveforce</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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