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<title>pair_style list command &mdash; LAMMPS 17 Dec 2015 documentation</title>
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<div class="section" id="pair-style-list-command">
<span id="index-0"></span><h1>pair_style list command<a class="headerlink" href="#pair-style-list-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>pair_style list listfile cutoff keyword
</pre></div>
</div>
<ul class="simple">
<li>listfile = name of file with list of pairwise interactions</li>
<li>cutoff = global cutoff (distance units)</li>
<li>keyword = optional flag <em>nocheck</em> or <em>check</em> (default is <em>check</em>)</li>
</ul>
</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>pair_style list restraints.txt 200.0
pair_coeff * *
</pre></div>
</div>
<div class="highlight-python"><div class="highlight"><pre>pair_style hybrid/overlay lj/cut 1.1225 list pair_list.txt 300.0
pair_coeff * * lj/cut 1.0 1.0
pair_coeff 3* 3* list
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline"></a></h2>
<p>Style <em>list</em> computes interactions between explicitly listed pairs of
atoms with the option to select functional form and parameters for
each individual pair. Because the parameters are set in the list
file, the pair_coeff command has no parameters (but still needs to be
provided). The <em>check</em> and <em>nocheck</em> keywords enable/disable a test
that checks whether all listed bonds were present and computed.</p>
<p>This pair style can be thought of as a hybrid between bonded,
non-bonded, and restraint interactions. It will typically be used as
an additional interaction within the <em>hybrid/overlay</em> pair style. It
currently supports three interaction styles: a 12-6 Lennard-Jones, a
Morse and a harmonic potential.</p>
<p>The format of the list file is as follows:</p>
<ul class="simple">
<li>one line per pair of atoms</li>
<li>empty lines will be ignored</li>
<li>comment text starts with a &#8216;#&#8217; character</li>
<li>line syntax: <em>ID1 ID2 style coeffs cutoff</em></li>
</ul>
<div class="highlight-python"><div class="highlight"><pre>ID1 = atom ID of first atom
ID2 = atom ID of second atom
style = style of interaction
coeffs = list of coeffs
cutoff = cutoff for interaction (optional)
</pre></div>
</div>
<p>The cutoff parameter is optional. If not specified, the global cutoff
is used.</p>
<p>Here is an example file:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="c"># this is a comment</span>
</pre></div>
</div>
<div class="highlight-python"><div class="highlight"><pre>15 259 lj126 1.0 1.0 50.0
15 603 morse 10.0 1.2 2.0 10.0 # and another comment
18 470 harmonic 50.0 1.2 5.0
</pre></div>
</div>
<p>The style <em>lj126</em> computes pairwise interactions with the formula</p>
<img alt="_images/pair_lj.jpg" class="align-center" src="_images/pair_lj.jpg" />
<p>and the coefficients:</p>
<ul class="simple">
<li>epsilon (energy units)</li>
<li>sigma (distance units)</li>
</ul>
<p>The style <em>morse</em> computes pairwise interactions with the formula</p>
<img alt="_images/pair_morse.jpg" class="align-center" src="_images/pair_morse.jpg" />
<p>and the coefficients:</p>
<ul class="simple">
<li>D0 (energy units)</li>
<li>alpha (1/distance units)</li>
<li>r0 (distance units)</li>
</ul>
<p>The style <em>harmonic</em> computes pairwise interactions with the formula</p>
<img alt="_images/bond_harmonic.jpg" class="align-center" src="_images/bond_harmonic.jpg" />
<p>and the coefficients:</p>
<ul class="simple">
<li>K (energy units)</li>
<li>r0 (distance units)</li>
</ul>
<p>Note that the usual 1/2 factor is included in K.</p>
<hr class="docutils" />
<p><strong>Mixing, shift, table, tail correction, restart, rRESPA info</strong>:</p>
<p>This pair style does not support mixing since all parameters are
explicit for each pair.</p>
<p>The <a class="reference internal" href="pair_modify.html"><em>pair_modify</em></a> shift option is supported by this
pair style.</p>
<p>The <a class="reference internal" href="pair_modify.html"><em>pair_modify</em></a> table and tail options are not
relevant for this pair style.</p>
<p>This pair style does not write its information to <a class="reference internal" href="restart.html"><em>binary restart files</em></a>, so pair_style and pair_coeff commands 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"><em>run_style respa</em></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<a class="headerlink" href="#restrictions" title="Permalink to this headline"></a></h2>
<p>This pair style does not use a neighbor list and instead identifies
atoms by their IDs. This has two consequences: 1) The cutoff has to be
chosen sufficiently large, so that the second atom of a pair has to be
a ghost atom on the same node on which the first atom is local;
otherwise the interaction will be skipped. You can use the <em>check</em>
option to detect, if interactions are missing. 2) Unlike other pair
styles in LAMMPS, an atom I will not interact with multiple images of
atom J (assuming the images are within the cutoff distance), but only
with the nearest image.</p>
<p>This style is part of the USER-MISC package. It is only enabled if
LAMMPS is build with that package. See the <span class="xref std std-ref">Making of LAMMPS</span> section for more info.</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="pair_coeff.html"><em>pair_coeff</em></a>,
<a class="reference internal" href="pair_hybrid.html"><em>pair_style hybrid/overlay</em></a>,
<a class="reference internal" href="pair_lj.html"><em>pair_style lj/cut</em></a>,
<a class="reference internal" href="pair_morse.html"><em>pair_style morse</em></a>,
<a class="reference internal" href="bond_harmonic.html"><em>bond_style harmonic</em></a></p>
<p><strong>Default:</strong> none</p>
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