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<div class="section" id="pair-style-lj-expand-command">
<span id="index-0"></span><h1>pair_style lj/expand command</h1>
</div>
<div class="section" id="pair-style-lj-expand-gpu-command">
<h1>pair_style lj/expand/gpu command</h1>
</div>
<div class="section" id="pair-style-lj-expand-omp-command">
<h1>pair_style lj/expand/omp command</h1>
<div class="section" id="syntax">
<h2>Syntax</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">pair_style</span> <span class="n">lj</span><span class="o">/</span><span class="n">expand</span> <span class="n">cutoff</span>
</pre></div>
</div>
<ul class="simple">
<li>cutoff = global cutoff for lj/expand interactions (distance units)</li>
</ul>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">pair_style</span> <span class="n">lj</span><span class="o">/</span><span class="n">expand</span> <span class="mf">2.5</span>
<span class="n">pair_coeff</span> <span class="o">*</span> <span class="o">*</span> <span class="mf">1.0</span> <span class="mf">1.0</span> <span class="mf">0.5</span>
<span class="n">pair_coeff</span> <span class="mi">1</span> <span class="mi">1</span> <span class="mf">1.0</span> <span class="mf">1.0</span> <span class="o">-</span><span class="mf">0.2</span> <span class="mf">2.0</span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>Style <em>lj/expand</em> computes a LJ interaction with a distance shifted by
delta which can be useful when particles are of different sizes, since
it is different that using different sigma values in a standard LJ
formula:</p>
<img alt="_images/pair_lj_expand.jpg" class="align-center" src="_images/pair_lj_expand.jpg" />
<p>Rc is the cutoff which does not include the delta distance. I.e. the
actual force cutoff is the sum of cutoff + delta.</p>
<p>The following coefficients must be defined for each pair of atoms
types via the <a class="reference internal" href="pair_coeff.html"><span class="doc">pair_coeff</span></a> command as in the examples
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, or by mixing as described below:</p>
<ul class="simple">
<li>epsilon (energy units)</li>
<li>sigma (distance units)</li>
<li>delta (distance units)</li>
<li>cutoff (distance units)</li>
</ul>
<p>The delta values can be positive or negative. The last coefficient is
optional. If not specified, the global LJ cutoff is used.</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>
<hr class="docutils" />
<p><strong>Mixing, shift, table, tail correction, restart, rRESPA info</strong>:</p>
<p>For atom type pairs I,J and I != J, the epsilon, sigma, and shift
coefficients and cutoff distance for this pair style can be mixed.
Shift is always mixed via an <em>arithmetic</em> rule. The other
coefficients are mixed according to the pair_modify mix value. The
default mix value is <em>geometric</em>. See the &#8220;pair_modify&#8221; command for
details.</p>
<p>This pair style supports the <a class="reference internal" href="pair_modify.html"><span class="doc">pair_modify</span></a> shift
option for the energy of the pair interaction.</p>
<p>The <a class="reference internal" href="pair_modify.html"><span class="doc">pair_modify</span></a> table option is not relevant
for this pair style.</p>
<p>This pair style supports the <a class="reference internal" href="pair_modify.html"><span class="doc">pair_modify</span></a> tail
option for adding a long-range tail correction to the energy and
pressure of the pair interaction.</p>
<p>This pair style writes its information to <a class="reference internal" href="restart.html"><span class="doc">binary restart files</span></a>, so pair_style and pair_coeff commands do not need
to be specified in an input script that reads a restart file.</p>
<p>This pair style can only be used via the <em>pair</em> keyword of the
<a class="reference internal" href="run_style.html"><span class="doc">run_style respa</span></a> command. It does not support the
<em>inner</em>, <em>middle</em>, <em>outer</em> keywords.</p>
</div>
<hr class="docutils" />
<div class="section" id="restrictions">
<h2>Restrictions</h2>
<blockquote>
<div>none</div></blockquote>
</div>
<div class="section" id="related-commands">
<h2>Related commands</h2>
<p><a class="reference internal" href="pair_coeff.html"><span class="doc">pair_coeff</span></a></p>
<p><strong>Default:</strong> none</p>
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