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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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<H3>dihedral_style hybrid command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>dihedral_style hybrid style1 style2 ...
</PRE>
<UL><LI>style1,style2 = list of one or more dihedral styles
</UL>
<P><B>Examples:</B>
</P>
<PRE>dihedral_style hybrid harmonic helix
dihedral_coeff 1 harmonic 6.0 1 3
dihedral_coeff 2* helix 10 10 10
</PRE>
<P><B>Description:</B>
</P>
<P>The <I>hybrid</I> style enables the use of multiple dihedral styles in one
simulation. An dihedral style is assigned to each dihedral type. For
example, dihedrals in a polymer flow (of dihedral type 1) could be
computed with a <I>harmonic</I> potential and dihedrals in the wall
boundary (of dihedral type 2) could be computed with a <I>helix</I>
potential. The assignment of dihedral type to style is made via the
<A HREF = "dihedral_coeff.html">dihedral_coeff</A> command or in the data file.
</P>
<P>In the dihedral_coeff commands, the name of a dihedral style must be
added after the dihedral type, with the remaining coefficients being
those appropriate to that style. In the example above, the 2
dihedral_coeff commands set dihedrals of dihedral type 1 to be
computed with a <I>harmonic</I> potential with coefficients 6.0, 1, 3 for
K, d, n. All other dihedral types (2-N) are computed with a <I>helix</I>
potential with coefficients 10, 10, 10 for A, B, C.
</P>
<P>If dihedral coefficients are specified in the data file read via the
<A HREF = "read_data.html">read_data</A> command, then the same rule applies.
E.g. "harmonic" or "helix", must be added after the dihedral type, for
each line in the "Dihedral Coeffs" section, e.g.
</P>
<PRE>Dihedral Coeffs
</PRE>
<PRE>1 harmonic 6.0 1 3
2 helix 10 10 10
...
</PRE>
<P>If <I>class2</I> is one of the dihedral hybrid styles, the same rule holds
for specifying additional AngleTorsion (and EndBondTorsion, etc)
coefficients either via the input script or in the data file.
I.e. <I>class2</I> must be added to each line after the dihedral type. For
lines in the AngleTorsion (or EndBondTorsion, etc) section of the data
file for dihedral types that are not <I>class2</I>, you must use an
dihedral style of <I>skip</I> as a placeholder, e.g.
</P>
<PRE>AngleTorsion Coeffs
</PRE>
<PRE>1 skip
2 class2 1.0 1.0 1.0 3.0 3.0 3.0 30.0 50.0
...
</PRE>
<P>Note that it is not necessary to use the dihedral style <I>skip</I> in the
input script, since AngleTorsion (or EndBondTorsion, etc) coefficients
need not be specified at all for dihedral types that are not <I>class2</I>.
</P>
<P>A dihedral style of <I>none</I> with no additional coefficients can be used
in place of a dihedral style, either in a input script dihedral_coeff
command or in the data file, if you desire to turn off interactions
for specific dihedral types.
</P>
<HR>
<P><B>Restrictions:</B>
</P>
<P>This dihedral style can only be used if LAMMPS was built with the
MOLECULE package (which it is by default). See the <A HREF = "Section_start.html#start_3">Making
LAMMPS</A> section for more info on packages.
</P>
<P>Unlike other dihedral styles, the hybrid dihedral style does not store
dihedral coefficient info for individual sub-styles in a <A HREF = "restart.html">binary
restart files</A>. Thus when retarting a simulation from a
restart file, you need to re-specify dihedral_coeff commands.
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "dihedral_coeff.html">dihedral_coeff</A>
</P>
<P><B>Default:</B> none
</P>
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