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angle_cmm.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>angle_style cg/cmm command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>angle_style cg/cmm
</PRE>
<P><B>Examples:</B>
</P>
<PRE>angle_style cg/cmm
angle_coeff 1 300.0 107.0 lj9_6 0.4491 3.7130
</PRE>
<P><B>Description:</B>
</P>
<P>The <I>cg/cmm</I> angle style is a combination of the harmonic angle potential,
</P>
<CENTER><IMG SRC = "Eqs/angle_harmonic.jpg">
</CENTER>
<P>where theta0 is the equilibrium value of the angle and K a prefactor,
with the <I>repulsive</I> part of the non-bonded <I>cg/cmm</I> pair style
between the atoms 1 and 3. This angle potential is intended for
coarse grained MD simulations with the CMM parametrization using the
<A HREF = "pair_cmm.html">pair_style cg/cmm</A>. Relative to the pair_style
<I>cg/cmm</I>, however, the energy is shifted by <I>epsilon</I>, to avoid sudden
jumps. 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. As
with other CMM coarse grained parameters, they cannot be set in the
data file, but can be restored from restarts via the
<A HREF = "read_restart.html">read_restart</A> command:
</P>
<UL><LI>K (energy/radian^2)
<LI>theta0 (degrees)
<LI>cg_type (string, one of lj9_6, lj12_4, lj12_6)
<LI>epsilon (energy units)
<LI>sigma (distance units)
</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>
<P><B>Restrictions:</B>
</P>
<P>This angle style can only be used if LAMMPS was built with the
"user-cg-cmm" package. See the <A HREF = "Section_start.html#2_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>, <A HREF = "angle_harmonic.html">angle_style
harmonic</A>, <A HREF = "pair_cmm.html">pair_style cg/cmm</A>
</P>
<P><B>Default:</B> none
</P>
</HTML>

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