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<li class="toctree-l2"><a class="reference internal" href="dihedral_charmm.html#dihedral-style-charmm-intel-command">dihedral_style charmm/intel command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_charmm.html#dihedral-style-charmm-kk-command">dihedral_style charmm/kk command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_charmm.html#dihedral-style-charmm-omp-command">dihedral_style charmm/omp command</a></li>
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<li class="toctree-l2 current"><a class="current reference internal" href="#">dihedral_style harmonic command</a></li>
<li class="toctree-l2"><a class="reference internal" href="#dihedral-style-harmonic-intel-command">dihedral_style harmonic/intel command</a></li>
<li class="toctree-l2"><a class="reference internal" href="#dihedral-style-harmonic-omp-command">dihedral_style harmonic/omp command</a><ul>
<li class="toctree-l3"><a class="reference internal" href="#syntax">Syntax</a></li>
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<li class="toctree-l2"><a class="reference internal" href="dihedral_helix.html">dihedral_style helix command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="dihedral_multi_harmonic.html">dihedral_style multi/harmonic command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_multi_harmonic.html#dihedral-style-multi-harmonic-omp-command">dihedral_style multi/harmonic/omp command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_nharmonic.html">dihedral_style nharmonic command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="dihedral_charmm.html#dihedral-style-charmm-kk-command">dihedral_style charmm/kk command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_charmm.html#dihedral-style-charmm-omp-command">dihedral_style charmm/omp command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_class2.html">dihedral_style class2 command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_class2.html#dihedral-style-class2-omp-command">dihedral_style class2/omp command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_cosine_shift_exp.html">dihedral_style cosine/shift/exp command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_cosine_shift_exp.html#dihedral-style-cosine-shift-exp-omp-command">dihedral_style cosine/shift/exp/omp command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_fourier.html">dihedral_style fourier command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_fourier.html#dihedral-style-fourier-omp-command">dihedral_style fourier/omp command</a></li>
<li class="toctree-l2 current"><a class="current reference internal" href="#">dihedral_style harmonic command</a></li>
<li class="toctree-l2"><a class="reference internal" href="#dihedral-style-harmonic-intel-command">dihedral_style harmonic/intel command</a></li>
<li class="toctree-l2"><a class="reference internal" href="#dihedral-style-harmonic-omp-command">dihedral_style harmonic/omp command</a><ul>
<li class="toctree-l3"><a class="reference internal" href="#syntax">Syntax</a></li>
<li class="toctree-l3"><a class="reference internal" href="#examples">Examples</a></li>
<li class="toctree-l3"><a class="reference internal" href="#description">Description</a></li>
<li class="toctree-l3"><a class="reference internal" href="#restrictions">Restrictions</a></li>
<li class="toctree-l3"><a class="reference internal" href="#related-commands">Related commands</a></li>
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<li class="toctree-l2"><a class="reference internal" href="dihedral_helix.html">dihedral_style helix command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_helix.html#dihedral-style-helix-omp-command">dihedral_style helix/omp command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_hybrid.html">dihedral_style hybrid command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_multi_harmonic.html">dihedral_style multi/harmonic command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_multi_harmonic.html#dihedral-style-multi-harmonic-omp-command">dihedral_style multi/harmonic/omp command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_nharmonic.html">dihedral_style nharmonic command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_nharmonic.html#dihedral-style-nharmonic-omp-command">dihedral_style nharmonic/omp command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_none.html">dihedral_style none command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_opls.html">dihedral_style opls command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_opls.html#dihedral-style-opls-intel-command">dihedral_style opls/intel command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_opls.html#dihedral-style-opls-kk-command">dihedral_style opls/kk command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_opls.html#dihedral-style-opls-omp-command">dihedral_style opls/omp command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_quadratic.html">dihedral_style quadratic command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_quadratic.html#dihedral-style-quadratic-omp-command">dihedral_style quadratic/omp command</a></li>
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<div class="section" id="dihedral-style-harmonic-command">
<span id="index-0"></span><h1>dihedral_style harmonic command</h1>
</div>
<div class="section" id="dihedral-style-harmonic-intel-command">
<h1>dihedral_style harmonic/intel command</h1>
</div>
<div class="section" id="dihedral-style-harmonic-omp-command">
<h1>dihedral_style harmonic/omp command</h1>
<div class="section" id="syntax">
<h2>Syntax</h2>
<pre class="literal-block">
dihedral_style harmonic
</pre>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<pre class="literal-block">
dihedral_style harmonic
dihedral_coeff 1 80.0 1 2
</pre>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>The <em>harmonic</em> dihedral style uses the potential</p>
<img alt="_images/dihedral_harmonic.jpg" class="align-center" src="_images/dihedral_harmonic.jpg" />
<p>The following coefficients must be defined for each dihedral type via the
<a class="reference internal" href="dihedral_coeff.html"><span class="doc">dihedral_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>K (energy)</li>
<li>d (+1 or -1)</li>
<li>n (integer &gt;= 0)</li>
</ul>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Here are important points to take note of when defining LAMMPS
dihedral coefficients for the harmonic style, so that they are
compatible with how harmonic dihedrals are defined by other force
fields:</p>
</div>
<ul class="simple">
<li>The LAMMPS convention is that the trans position = 180 degrees, while
in some force fields trans = 0 degrees.</li>
<li>Some force fields reverse the sign convention on <em>d</em>.</li>
<li>Some force fields let <em>n</em> be positive or negative which corresponds to
<em>d</em> = 1 or -1 for the harmonic style.</li>
</ul>
<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 5</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 5</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 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>
</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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