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<div class="section" id="angle-style-cosine-periodic-command">
<span id="index-0"></span><h1>angle_style cosine/periodic command</h1>
</div>
<div class="section" id="angle-style-cosine-periodic-omp-command">
<h1>angle_style cosine/periodic/omp command</h1>
<div class="section" id="syntax">
<h2>Syntax</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">angle_style</span> <span class="n">cosine</span><span class="o">/</span><span class="n">periodic</span>
</pre></div>
</div>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">angle_style</span> <span class="n">cosine</span><span class="o">/</span><span class="n">periodic</span>
<span class="n">angle_coeff</span> <span class="o">*</span> <span class="mf">75.0</span> <span class="mi">1</span> <span class="mi">6</span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>The <em>cosine/periodic</em> angle style uses the following potential, which
is commonly used in the <a class="reference internal" href="Section_howto.html#howto-4"><span class="std std-ref">DREIDING</span></a> force
field, particularly for organometallic systems where <em>n</em> = 4 might be
used for an octahedral complex and <em>n</em> = 3 might be used for a
trigonal center:</p>
<img alt="_images/angle_cosine_periodic.jpg" class="align-center" src="_images/angle_cosine_periodic.jpg" />
<p>where C, B and n are coefficients defined for each angle type.</p>
<p>See <a class="reference internal" href="#cosine-mayo"><span class="std std-ref">(Mayo)</span></a> for a description of the DREIDING force field</p>
<p>The following coefficients must be defined for each angle type via the
<a class="reference internal" href="angle_coeff.html"><span class="doc">angle_coeff</span></a> command as in the example above, or in
the data file or restart files read by the <a class="reference internal" href="read_data.html"><span class="doc">read_data</span></a>
or <a class="reference internal" href="read_restart.html"><span class="doc">read_restart</span></a> commands:</p>
<ul class="simple">
<li>C (energy)</li>
<li>B = 1 or -1</li>
<li>n = 1, 2, 3, 4, 5 or 6 for periodicity</li>
</ul>
<p>Note that the prefactor C is specified and not the overall force
constant K = C / n^2. When B = 1, it leads to a minimum for the
linear geometry. When B = -1, it leads to a maximum for the linear
geometry.</p>
<hr class="docutils" />
<p>Styles with a <em>gpu</em>, <em>intel</em>, <em>kk</em>, <em>omp</em>, or <em>opt</em> suffix are
functionally the same as the corresponding style without the suffix.
They have been optimized to run faster, depending on your available
hardware, as discussed in <a class="reference internal" href="Section_accelerate.html"><span class="doc">Section_accelerate</span></a>
of the manual. The accelerated styles take the same arguments and
should produce the same results, except for round-off and precision
issues.</p>
<p>These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
USER-OMP and OPT packages, respectively. They are only enabled if
LAMMPS was built with those packages. 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.</p>
<p>You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the <a class="reference internal" href="Section_start.html#start-7"><span class="std std-ref">-suffix command-line switch</span></a> when you invoke LAMMPS, or you can
use the <a class="reference internal" href="suffix.html"><span class="doc">suffix</span></a> command in your input script.</p>
<p>See <a class="reference internal" href="Section_accelerate.html"><span class="doc">Section_accelerate</span></a> of the manual for
more instructions on how to use the accelerated styles effectively.</p>
</div>
<hr class="docutils" />
<div class="section" id="restrictions">
<h2>Restrictions</h2>
<p>This angle 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>
</div>
<div class="section" id="related-commands">
<h2>Related commands</h2>
<p><a class="reference internal" href="angle_coeff.html"><span class="doc">angle_coeff</span></a></p>
<p><strong>Default:</strong> none</p>
<hr class="docutils" />
<p id="cosine-mayo"><strong>(Mayo)</strong> Mayo, Olfason, Goddard III, J Phys Chem, 94, 8897-8909
(1990).</p>
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