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<div class="section" id="dihedral-style-hybrid-command">
<span id="index-0"></span><h1>dihedral_style hybrid command</h1>
<div class="section" id="syntax">
<h2>Syntax</h2>
<pre class="literal-block">
dihedral_style hybrid style1 style2 ...
</pre>
<ul class="simple">
<li>style1,style2 = list of one or more dihedral styles</li>
</ul>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<pre class="literal-block">
dihedral_style hybrid harmonic helix
dihedral_coeff 1 harmonic 6.0 1 3
dihedral_coeff 2* helix 10 10 10
</pre>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>The <em>hybrid</em> 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 <em>harmonic</em> potential and dihedrals in the wall
boundary (of dihedral type 2) could be computed with a <em>helix</em>
potential. The assignment of dihedral type to style is made via the
<a class="reference internal" href="dihedral_coeff.html"><span class="doc">dihedral_coeff</span></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 <em>harmonic</em> potential with coefficients 6.0, 1, 3 for
K, d, n. All other dihedral types (2-N) are computed with a <em>helix</em>
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 class="reference internal" href="read_data.html"><span class="doc">read_data</span></a> command, then the same rule applies.
E.g. &#8220;harmonic&#8221; or &#8220;helix&#8221;, must be added after the dihedral type, for
each line in the &#8220;Dihedral Coeffs&#8221; section, e.g.</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">Dihedral</span> <span class="n">Coeffs</span>
</pre></div>
</div>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="mi">1</span> <span class="n">harmonic</span> <span class="mf">6.0</span> <span class="mi">1</span> <span class="mi">3</span>
<span class="mi">2</span> <span class="n">helix</span> <span class="mi">10</span> <span class="mi">10</span> <span class="mi">10</span>
<span class="o">...</span>
</pre></div>
</div>
<p>If <em>class2</em> 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. <em>class2</em> 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 <em>class2</em>, you must use an
dihedral style of <em>skip</em> as a placeholder, e.g.</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">AngleTorsion</span> <span class="n">Coeffs</span>
</pre></div>
</div>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="mi">1</span> <span class="n">skip</span>
<span class="mi">2</span> <span class="n">class2</span> <span class="mf">1.0</span> <span class="mf">1.0</span> <span class="mf">1.0</span> <span class="mf">3.0</span> <span class="mf">3.0</span> <span class="mf">3.0</span> <span class="mf">30.0</span> <span class="mf">50.0</span>
<span class="o">...</span>
</pre></div>
</div>
<p>Note that it is not necessary to use the dihedral style <em>skip</em> in the
input script, since AngleTorsion (or EndBondTorsion, etc) coefficients
need not be specified at all for dihedral types that are not <em>class2</em>.</p>
<p>A dihedral style of <em>none</em> 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>
</div>
<hr class="docutils" />
<div class="section" id="restrictions">
<h2>Restrictions</h2>
<p>This dihedral style can only be used if LAMMPS was built with the
MOLECULE package (which it is by default). See the <a class="reference internal" href="Section_start.html#start-3"><span class="std std-ref">Making LAMMPS</span></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 class="reference internal" href="restart.html"><span class="doc">binary restart files</span></a>. Thus when retarting a simulation from a
restart file, you need to re-specify dihedral_coeff commands.</p>
</div>
<div class="section" id="related-commands">
<h2>Related commands</h2>
<p><a class="reference internal" href="dihedral_coeff.html"><span class="doc">dihedral_coeff</span></a></p>
<p><strong>Default:</strong> none</p>
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