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<div class="section" id="dihedral-style-harmonic-command">
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<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>
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<div class="section" id="dihedral-style-harmonic-omp-command">
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<h1>dihedral_style harmonic/omp command<a class="headerlink" href="#dihedral-style-harmonic-omp-command" title="Permalink to this headline">¶</a></h1>
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<div class="section" id="syntax">
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<h2>Syntax<a class="headerlink" href="#syntax" title="Permalink to this headline">¶</a></h2>
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<div class="highlight-python"><div class="highlight"><pre>dihedral_style harmonic
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</pre></div>
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</div>
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</div>
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<div class="section" id="examples">
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<h2>Examples<a class="headerlink" href="#examples" title="Permalink to this headline">¶</a></h2>
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<div class="highlight-python"><div class="highlight"><pre>dihedral_style harmonic
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dihedral_coeff 1 80.0 1 2
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</pre></div>
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</div>
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</div>
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<div class="section" id="description">
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<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
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<p>The <em>harmonic</em> dihedral style uses the potential</p>
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<img alt="_images/dihedral_harmonic.jpg" class="align-center" src="_images/dihedral_harmonic.jpg" />
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<p>The following coefficients must be defined for each dihedral type via the
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<a class="reference internal" href="dihedral_coeff.html"><em>dihedral_coeff</em></a> command as in the example above, or in
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the data file or restart files read by the <a class="reference internal" href="read_data.html"><em>read_data</em></a>
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or <a class="reference internal" href="read_restart.html"><em>read_restart</em></a> commands:</p>
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<ul class="simple">
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<li>K (energy)</li>
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<li>d (+1 or -1)</li>
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<li>n (integer >= 0)</li>
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</ul>
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<div class="admonition note">
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<p class="first admonition-title">Note</p>
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<p class="last">Here are important points to take note of when defining LAMMPS
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dihedral coefficients for the harmonic style, so that they are
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compatible with how harmonic dihedrals are defined by other force
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fields:</p>
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</div>
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<ul class="simple">
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<li>The LAMMPS convention is that the trans position = 180 degrees, while
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in some force fields trans = 0 degrees.</li>
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<li>Some force fields reverse the sign convention on <em>d</em>.</li>
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<li>Some force fields let <em>n</em> be positive or negative which corresponds to
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<em>d</em> = 1 or -1 for the harmonic style.</li>
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</ul>
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<hr class="docutils" />
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<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
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed in <a class="reference internal" href="Section_accelerate.html"><em>Section_accelerate</em></a>
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of the manual. The accelerated styles take the same arguments and
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should produce the same results, except for round-off and precision
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issues.</p>
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<p>These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
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KOKKOS, USER-OMP and OPT packages, respectively. They are only
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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>
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<p>You can specify the accelerated styles explicitly in your input script
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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
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use the <a class="reference internal" href="suffix.html"><em>suffix</em></a> command in your input script.</p>
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<p>See <a class="reference internal" href="Section_accelerate.html"><em>Section_accelerate</em></a> of the manual for
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more instructions on how to use the accelerated styles effectively.</p>
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</div>
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<div class="section" id="restrictions">
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<h2>Restrictions<a class="headerlink" href="#restrictions" title="Permalink to this headline">¶</a></h2>
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<p>This dihedral style can only be used if LAMMPS was built with the
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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>
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</div>
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<div class="section" id="related-commands">
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<h2>Related commands<a class="headerlink" href="#related-commands" title="Permalink to this headline">¶</a></h2>
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<p><a class="reference internal" href="dihedral_coeff.html"><em>dihedral_coeff</em></a></p>
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<p><strong>Default:</strong> none</p>
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