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>improper_style command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>improper_style style
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</PRE>
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<UL><LI>style = <I>none</I> or <I>hybrid</I> or <I>class2</I> or <I>cvff</I> or <I>harmonic</I>
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>improper_style harmonic
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improper_style cvff
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improper_style hybrid cvff harmonic
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Set the formula(s) LAMMPS uses to compute improper interactions
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between quadruplets of atoms, which remain in force for the duration
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of the simulation. The list of improper quadruplets is read in by a
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<A HREF = "read_data.html">read_data</A> or <A HREF = "read_restart.html">read_restart</A> command
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2007-06-28 23:07:55 +08:00
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from a data or restart file. Note that the ordering of the 4 atoms in
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an improper quadruplet determines the the definition of the improper
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angle used in the formula for each style. See the doc pages of
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individual styles for details.
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2006-09-22 00:22:34 +08:00
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</P>
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<P>Hybrid models where impropers are computed using different improper
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potentials can be setup using the <I>hybrid</I> improper style.
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</P>
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2007-06-25 22:36:36 +08:00
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<P>The coefficients associated with an improper style can be specified in
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a data or restart file or via the <A HREF = "improper_coeff.html">improper_coeff</A>
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command.
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2006-09-22 00:22:34 +08:00
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</P>
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2007-06-25 22:36:36 +08:00
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<P>All improper potentials store their coefficient data in binary restart
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files which means improper_style and
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<A HREF = "improper_coeff.html">improper_coeff</A> commands do not need to be
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re-specified in an input script that restarts a simulation. See the
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<A HREF = "read_restart.html">read_restart</A> command for details on how to do
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this. The one exception is that improper_style <I>hybrid</I> only stores
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the list of sub-styles in the restart file; improper coefficients need
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to be re-specified.
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</P>
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<P>IMPORTANT NOTE: When both an improper and pair style is defined, the
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<A HREF = "special_bonds.html">special_bonds</A> command often needs to be used to
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turn off (or weight) the pairwise interaction that would otherwise
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2007-06-28 23:07:55 +08:00
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exist between a group of 4 bonded atoms.
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2006-09-22 00:22:34 +08:00
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</P>
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<HR>
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<P>Here is an alphabetic list of improper styles defined in LAMMPS. Click on
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the style to display the formula it computes and coefficients
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specified by the associated <A HREF = "improper_coeff.html">improper_coeff</A> command:
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</P>
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2007-02-10 05:37:30 +08:00
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<UL><LI><A HREF = "improper_none.html">improper_style none</A> - turn off improper interactions
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<LI><A HREF = "improper_hybrid.html">improper_style hybrid</A> - define multiple styles of improper interactions
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</UL>
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2007-02-10 05:37:30 +08:00
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<UL><LI><A HREF = "improper_class2.html">improper_style class2</A> - COMPASS (class 2) improper
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<LI><A HREF = "improper_cvff.html">improper_style cvff</A> - CVFF improper
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<LI><A HREF = "improper_harmonic.html">improper_style harmonic</A> - harmonic improper
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</UL>
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2009-11-05 06:12:52 +08:00
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<P>There are also additional improper styles submitted by users which are
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included in the LAMMPS distribution. The list of these with links to
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the individual styles are given in the improper section of <A HREF = "Section_commands.html#3_5">this
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page</A>.
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</P>
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2006-09-22 00:22:34 +08:00
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<HR>
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<P><B>Restrictions:</B>
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</P>
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<P>Improper styles can only be set for atom_style choices that allow
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impropers to be defined.
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</P>
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2007-06-25 22:36:36 +08:00
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<P>Most improper styles are part of the "molecular" package. They are
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only enabled if 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 on packages. The
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doc pages for individual improper potentials tell if it is part of a
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package.
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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>
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</P>
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<P><A HREF = "improper_coeff.html">improper_coeff</A>
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</P>
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<P><B>Default:</B>
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</P>
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<PRE>improper_style none
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</PRE>
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</HTML>
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