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<div class="section" id="dihedral-style-harmonic-command">
<span id="index-0"></span><h1>dihedral_style harmonic command<a class="headerlink" href="#dihedral-style-harmonic-command" title="Permalink to this headline">¶</a></h1>
</div>
<div class="section" id="dihedral-style-harmonic-omp-command">
<h1>dihedral_style harmonic/omp command<a class="headerlink" href="#dihedral-style-harmonic-omp-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>dihedral_style harmonic
</pre></div>
</div>
</div>
<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>dihedral_style harmonic
dihedral_coeff 1 80.0 1 2
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></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"><em>dihedral_coeff</em></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"><em>read_data</em></a>
or <a class="reference internal" href="read_restart.html"><em>read_restart</em></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 warning">
<p class="first admonition-title">Warning</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>cuda</em>, <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"><em>Section_accelerate</em></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 USER-CUDA, 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>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>-suffix command-line switch</span></a> when you invoke LAMMPS, or you can
use the <a class="reference internal" href="suffix.html"><em>suffix</em></a> command in your input script.</p>
<p>See <a class="reference internal" href="Section_accelerate.html"><em>Section_accelerate</em></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<a class="headerlink" href="#restrictions" title="Permalink to this headline">¶</a></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>Making LAMMPS</span></a> section for more info on packages.</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="dihedral_coeff.html"><em>dihedral_coeff</em></a></p>
<p><strong>Default:</strong> none</p>
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