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improper_style_harmonic.html
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<HTML>
<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>
<HR>
<H3>improper_style harmonic command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>improper_style harmonic
</PRE>
<P><B>Examples:</B>
</P>
<PRE>improper_style harmonic
improper_coeff 1 100.0 0
</PRE>
<P><B>Description:</B>
</P>
<P>The <I>harmonic</I> improper style uses the potential
</P>
<CENTER><IMG SRC = "Eqs/improper_harmonic.jpg">
</CENTER>
<P>where X is the improper angle, X0 is its equilibrium value, and K is a
prefactor. Note that the usual 1/2 factor is included in K.
</P>
<P>The following coefficients must be defined for each improper type via the
<A HREF = "improper_coeff.html">improper_coeff</A> command as in the example above, or in
the data file or restart files read by the <A HREF = "read_data.html">read_data</A>
or <A HREF = "read_restart.html">read_restart</A> commands:
</P>
<UL><LI>K (energy/radian^2)
<LI>X0 (degrees)
</UL>
<P>X0 is specified in degrees, but LAMMPS converts it to radians
internally; hence the units of K are in energy/radian^2.
</P>
<P><B>Restrictions:</B>
</P>
<P>Improper styles can only be set for atom styles that allow impropers to be
defined.
</P>
<P>This improper style is part of the "molecular" package. It is only
enabled if LAMMPS was built with that package. See the <A HREF = "Section_start.html#2_2">Making
LAMMPS</A> section for more info.
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "improper_coeff.html">improper_coeff</A>
</P>
<P><B>Default:</B> none
</P>
</HTML>

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