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<li class="toctree-l1"><a class="reference internal" href="Section_intro.html">1. Introduction</a></li>
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<li class="toctree-l1"><a class="reference internal" href="Section_start.html">2. Getting Started</a></li>
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<li class="toctree-l1"><a class="reference internal" href="Section_accelerate.html">5. Accelerating LAMMPS performance</a></li>
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<div class="section" id="pair-style-edip-command">
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<span id="index-0"></span><h1>pair_style edip command<a class="headerlink" href="#pair-style-edip-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>pair_style edip
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</pre></div>
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</div>
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<div class="highlight-python"><div class="highlight"><pre>pair_style edip/omp
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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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<p>pair_style edip
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pair_coeff * * Si.edip Si</p>
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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>edip</em> style computes a 3-body <a class="reference internal" href="#edip"><span>EDIP</span></a> potential which is
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popular for modeling silicon materials where it can have advantages
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over other models such as the <a class="reference internal" href="pair_sw.html"><em>Stillinger-Weber</em></a> or
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<a class="reference internal" href="pair_tersoff.html"><em>Tersoff</em></a> potentials. In EDIP, the energy E of a
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system of atoms is</p>
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<img alt="_images/pair_edip.jpg" class="align-center" src="_images/pair_edip.jpg" />
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<p>where phi2 is a two-body term and phi3 is a three-body term. The
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summations in the formula are over all neighbors J and K of atom I
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within a cutoff distance = a.
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Both terms depend on the local environment of atom I through its
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effective coordination number defined by Z, which is unity for a
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cutoff distance < c and gently goes to 0 at distance = a.</p>
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<p>Only a single pair_coeff command is used with the <em>edip</em> style which
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specifies a EDIP potential file with parameters for all
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needed elements. These are mapped to LAMMPS atom types by specifying
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N additional arguments after the filename in the pair_coeff command,
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where N is the number of LAMMPS atom types:</p>
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<ul class="simple">
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<li>filename</li>
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<li>N element names = mapping of EDIP elements to atom types</li>
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</ul>
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<p>See the <a class="reference internal" href="pair_coeff.html"><em>pair_coeff</em></a> doc page for alternate ways
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to specify the path for the potential file.</p>
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<p>As an example, imagine a file Si.edip has EDIP values for Si.</p>
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<p>EDIP files in the <em>potentials</em> directory of the LAMMPS
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distribution have a ”.edip” suffix. Lines that are not blank or
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comments (starting with #) define parameters for a triplet of
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elements. The parameters in a single entry correspond to the two-body
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and three-body coefficients in the formula above:</p>
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<ul class="simple">
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<li>element 1 (the center atom in a 3-body interaction)</li>
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<li>element 2</li>
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<li>element 3</li>
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<li>A (energy units)</li>
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<li>B (distance units)</li>
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<li>cutoffA (distance units)</li>
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<li>cutoffC (distance units)</li>
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<li>alpha</li>
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<li>beta</li>
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<li>eta</li>
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<li>gamma (distance units)</li>
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<li>lambda (energy units)</li>
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<li>mu</li>
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<li>tho</li>
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<li>sigma (distance units)</li>
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<li>Q0</li>
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<li>u1</li>
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<li>u2</li>
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<li>u3</li>
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<li>u4</li>
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</ul>
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<p>The A, B, beta, sigma parameters are used only for two-body interactions.
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The eta, gamma, lambda, mu, Q0 and all u1 to u4 parameters are used only
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for three-body interactions. The alpha and cutoffC parameters are used
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for the coordination environment function only.</p>
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<p>The EDIP potential file must contain entries for all the
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elements listed in the pair_coeff command. It can also contain
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entries for additional elements not being used in a particular
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simulation; LAMMPS ignores those entries.</p>
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<p>For a single-element simulation, only a single entry is required
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(e.g. SiSiSi). For a two-element simulation, the file must contain 8
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entries (for SiSiSi, SiSiC, SiCSi, SiCC, CSiSi, CSiC, CCSi, CCC), that
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specify EDIP parameters for all permutations of the two elements
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interacting in three-body configurations. Thus for 3 elements, 27
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entries would be required, etc.</p>
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<p>At the moment, only a single element parametrization is
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implemented. However, the author is not aware of other
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multi-element EDIP parametrizations. If you know any and
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you are interest in that, please contact the author of
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the EDIP package.</p>
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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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<hr class="docutils" />
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<p><strong>Mixing, shift, table, tail correction, restart, rRESPA info</strong>:</p>
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<p>This pair style does not support the <a class="reference internal" href="pair_modify.html"><em>pair_modify</em></a>
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shift, table, and tail options.</p>
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<p>This pair style does not write its information to <a class="reference internal" href="restart.html"><em>binary restart files</em></a>, since it is stored in potential files. Thus, you
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need to re-specify the pair_style and pair_coeff commands in an input
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script that reads a restart file.</p>
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<p>This pair style can only be used via the <em>pair</em> keyword of the
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<a class="reference internal" href="run_style.html"><em>run_style respa</em></a> command. It does not support the
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<em>inner</em>, <em>middle</em>, <em>outer</em> keywords.</p>
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</div>
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<hr class="docutils" />
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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 angle style can only be used if LAMMPS was built with the
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USER-MISC package. See the <a class="reference internal" href="Section_start.html#start-3"><span>Making LAMMPS</span></a>
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section for more info on packages.</p>
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<p>This pair style requires the <a class="reference internal" href="newton.html"><em>newton</em></a> setting to be “on”
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for pair interactions.</p>
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<p>The EDIP potential files provided with LAMMPS (see the potentials directory)
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are parameterized for metal <a class="reference internal" href="units.html"><em>units</em></a>.
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You can use the SW potential with any LAMMPS units, but you would need
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to create your own EDIP potential file with coefficients listed in the
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appropriate units if your simulation doesn’t use “metal” units.</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="pair_coeff.html"><em>pair_coeff</em></a></p>
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<p><strong>Default:</strong> none</p>
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<hr class="docutils" />
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<p id="edip"><strong>(EDIP)</strong> J. F. Justo et al., Phys. Rev. B 58, 2539 (1998).</p>
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