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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>angle_style quartic command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>angle_style quartic
</PRE>
<P><B>Examples:</B>
</P>
<PRE>angle_style quartic
angle_coeff 1 129.1948 56.8726 -25.9442 -14.2221
</PRE>
<P><B>Description:</B>
</P>
<P>The <I>quartic</I> angle style uses the potential
</P>
<CENTER><IMG SRC = "Eqs/angle_quartic.jpg">
</CENTER>
<P>where theta0 is the equilibrium value of the angle, 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 angle type via the
<A HREF = "angle_coeff.html">angle_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>theta0 (degrees)
<LI>K2 (energy/radian^2)
<LI>K3 (energy/radian^3)
<LI>K4 (energy/radian^4)
</UL>
<P>Theta0 is specified in degrees, but LAMMPS converts it to radians
internally; hence the units of K are in energy/radian^2.
</P>
<HR>
<P><B>Restrictions:</B>
</P>
<P>This angle style can only be used if LAMMPS was built with the
USER_MISC package. See the <A HREF = "Section_start.html#start_3">Making LAMMPS</A>
section for more info on packages.
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "angle_coeff.html">angle_coeff</A>
</P>
<P><B>Default:</B> none
</P>
</HTML>