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<div class="section" id="improper-style-hybrid-command">
<span id="index-0"></span><h1>improper_style hybrid command<a class="headerlink" href="#improper-style-hybrid-command" title="Permalink to this headline"></a></h1>
<div class="section" id="syntax">
<h2>Syntax<a class="headerlink" href="#syntax" title="Permalink to this headline"></a></h2>
<div class="highlight-python"><div class="highlight"><pre>improper_style hybrid style1 style2 ...
</pre></div>
</div>
<ul class="simple">
<li>style1,style2 = list of one or more improper styles</li>
</ul>
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<div class="section" id="examples">
<h2>Examples<a class="headerlink" href="#examples" title="Permalink to this headline"></a></h2>
<div class="highlight-python"><div class="highlight"><pre>improper_style hybrid harmonic helix
improper_coeff 1 harmonic 120.0 30
improper_coeff 2 cvff 20.0 -1 2
</pre></div>
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<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline"></a></h2>
<p>The <em>hybrid</em> style enables the use of multiple improper styles in one
simulation. An improper style is assigned to each improper type. For
example, impropers in a polymer flow (of improper type 1) could be
computed with a <em>harmonic</em> potential and impropers in the wall
boundary (of improper type 2) could be computed with a <em>cvff</em>
potential. The assignment of improper type to style is made via the
<a class="reference internal" href="improper_coeff.html"><em>improper_coeff</em></a> command or in the data file.</p>
<p>In the improper_coeff command, the first coefficient sets the improper
style and the remaining coefficients are those appropriate to that
style. In the example above, the 2 improper_coeff commands would set
impropers of improper type 1 to be computed with a <em>harmonic</em>
potential with coefficients 120.0, 30 for K, X0. Improper type 2
would be computed with a <em>cvff</em> potential with coefficients 20.0, -1,
2 for K, d, n.</p>
<p>If the improper <em>class2</em> potential is one of the hybrid styles, it
requires additional AngleAngle coefficients be specified in the data
file. These lines must also have an additional &#8220;class2&#8221; argument
added after the improper type. For improper types which are assigned
to other hybrid styles, use the style name (e.g. &#8220;harmonic&#8221;)
appropriate to that style. The AngleAngle coeffs for that improper
type will then be ignored.</p>
<p>An improper style of <em>none</em> can be specified as the 2nd argument to
the improper_coeff command, if you desire to turn off certain improper
types.</p>
</div>
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<div class="section" id="restrictions">
<h2>Restrictions<a class="headerlink" href="#restrictions" title="Permalink to this headline"></a></h2>
<p>This improper 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>Making LAMMPS</span></a> section for more info on packages.</p>
<p>Unlike other improper styles, the hybrid improper style does not store
improper coefficient info for individual sub-styles in a <a class="reference internal" href="restart.html"><em>binary restart files</em></a>. Thus when retarting a simulation from a
restart file, you need to re-specify improper_coeff commands.</p>
</div>
<div class="section" id="related-commands">
<h2>Related commands<a class="headerlink" href="#related-commands" title="Permalink to this headline"></a></h2>
<p><a class="reference internal" href="improper_coeff.html"><em>improper_coeff</em></a></p>
<p><strong>Default:</strong> none</p>
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