Homec4science
Diffusion lammps (lammm-master) Browse

lammps/doc/html/compute_pair.html
7baaf2dfe210lammm-master

Last Change
Raw File

compute_pair.html
View Options

<!DOCTYPE html>
<!--[if IE 8]><html class="no-js lt-ie9" lang="en" > <![endif]-->
<!--[if gt IE 8]><!--> <html class="no-js" lang="en" > <!--<![endif]-->
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>compute pair command &mdash; LAMMPS documentation</title>
<link rel="stylesheet" href="_static/css/theme.css" type="text/css" />
<link rel="stylesheet" href="_static/sphinxcontrib-images/LightBox2/lightbox2/css/lightbox.css" type="text/css" />
<link rel="top" title="LAMMPS documentation" href="index.html"/>
<script src="_static/js/modernizr.min.js"></script>
</head>
<body class="wy-body-for-nav" role="document">
<div class="wy-grid-for-nav">
<nav data-toggle="wy-nav-shift" class="wy-nav-side">
<div class="wy-side-nav-search">
<a href="Manual.html" class="icon icon-home"> LAMMPS
</a>
<div role="search">
<form id="rtd-search-form" class="wy-form" action="search.html" method="get">
<input type="text" name="q" placeholder="Search docs" />
<input type="hidden" name="check_keywords" value="yes" />
<input type="hidden" name="area" value="default" />
</form>
</div>
</div>
<div class="wy-menu wy-menu-vertical" data-spy="affix" role="navigation" aria-label="main navigation">
<ul>
<li class="toctree-l1"><a class="reference internal" href="Section_intro.html">1. Introduction</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_start.html">2. Getting Started</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_commands.html">3. Commands</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_packages.html">4. Packages</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_accelerate.html">5. Accelerating LAMMPS performance</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_howto.html">6. How-to discussions</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_example.html">7. Example problems</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_perf.html">8. Performance &amp; scalability</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_tools.html">9. Additional tools</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_modify.html">10. Modifying &amp; extending LAMMPS</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_python.html">11. Python interface to LAMMPS</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_errors.html">12. Errors</a></li>
<li class="toctree-l1"><a class="reference internal" href="Section_history.html">13. Future and history</a></li>
</ul>
</div>
&nbsp;
</nav>
<section data-toggle="wy-nav-shift" class="wy-nav-content-wrap">
<nav class="wy-nav-top" role="navigation" aria-label="top navigation">
<i data-toggle="wy-nav-top" class="fa fa-bars"></i>
<a href="Manual.html">LAMMPS</a>
</nav>
<div class="wy-nav-content">
<div class="rst-content">
<div role="navigation" aria-label="breadcrumbs navigation">
<ul class="wy-breadcrumbs">
<li><a href="Manual.html">Docs</a> &raquo;</li>
<li>compute pair command</li>
<li class="wy-breadcrumbs-aside">
<a href="http://lammps.sandia.gov">Website</a>
<a href="Section_commands.html#comm">Commands</a>
</li>
</ul>
<hr/>
</div>
<div role="main" class="document" itemscope="itemscope" itemtype="http://schema.org/Article">
<div itemprop="articleBody">
<div class="section" id="compute-pair-command">
<span id="index-0"></span><h1>compute pair command</h1>
<div class="section" id="syntax">
<h2>Syntax</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">compute</span> <span class="n">ID</span> <span class="n">group</span><span class="o">-</span><span class="n">ID</span> <span class="n">pair</span> <span class="n">pstyle</span> <span class="n">evalue</span>
</pre></div>
</div>
<ul class="simple">
<li>ID, group-ID are documented in <a class="reference internal" href="compute.html"><span class="doc">compute</span></a> command</li>
<li>pair = style name of this compute command</li>
<li>pstyle = style name of a pair style that calculates additional values</li>
<li>evalue = <em>epair</em> or <em>evdwl</em> or <em>ecoul</em> or blank (optional setting)</li>
</ul>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">compute</span> <span class="mi">1</span> <span class="nb">all</span> <span class="n">pair</span> <span class="n">gauss</span>
<span class="n">compute</span> <span class="mi">1</span> <span class="nb">all</span> <span class="n">pair</span> <span class="n">lj</span><span class="o">/</span><span class="n">cut</span><span class="o">/</span><span class="n">coul</span><span class="o">/</span><span class="n">cut</span> <span class="n">ecoul</span>
<span class="n">compute</span> <span class="mi">1</span> <span class="nb">all</span> <span class="n">pair</span> <span class="n">reax</span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>Define a computation that extracts additional values calculated by a
pair style, and makes them accessible for output or further processing
by other commands. The group specified for this command is ignored.</p>
<p>The specified <em>pstyle</em> must be a pair style used in your simulation
either by itself or as a sub-style in a <a class="reference internal" href="pair_hybrid.html"><span class="doc">pair_style hybrid or hybrid/overlay</span></a> command.</p>
<p>The <em>evalue</em> setting is optional; it may be left off the command. All
pair styles tally a potential energy <em>epair</em> which may be broken into
two parts: <em>evdwl</em> and <em>ecoul</em> such that <em>epair</em> = <em>evdwl</em> + <em>ecoul</em>.
If the pair style calculates Coulombic interactions, their energy will
be tallied in <em>ecoul</em>. Everything else (whether it is a Lennard-Jones
style van der Waals interaction or not) is tallied in <em>evdwl</em>. If
<em>evalue</em> is specified as <em>epair</em> or left out, then <em>epair</em> is stored
as a global scalar by this compute. This is useful when using
<a class="reference internal" href="pair_hybrid.html"><span class="doc">pair_style hybrid</span></a> if you want to know the portion
of the total energy contributed by one sub-style. If <em>evalue</em> is
specfied as <em>evdwl</em> or <em>ecoul</em>, then just that portion of the energy
is stored as a global scalar.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The energy returned by the <em>evdwl</em> keyword does not include tail
corrections, even if they are enabled via the
<a class="reference internal" href="pair_modify.html"><span class="doc">pair_modify</span></a> command.</p>
</div>
<p>Some pair styles tally additional quantities, e.g. a breakdown of
potential energy into a dozen or so components is tallied by the
<a class="reference internal" href="pair_reax.html"><span class="doc">pair_style reax</span></a> commmand. These values (1 or more)
are stored as a global vector by this compute. See the doc page for
<a class="reference internal" href="pair_style.html"><span class="doc">individual pair styles</span></a> for info on these values.</p>
<p><strong>Output info:</strong></p>
<p>This compute calculates a global scalar which is <em>epair</em> or <em>evdwl</em> or
<em>ecoul</em>. If the pair style supports it, it also calculates a global
vector of length &gt;= 1, as determined by the pair style. These values
can be used by any command that uses global scalar or vector values
from a compute as input. See <a class="reference internal" href="Section_howto.html#howto-15"><span class="std std-ref">this section</span></a> for an overview of LAMMPS output
options.</p>
<p>The scalar and vector values calculated by this compute are
&#8220;extensive&#8221;.</p>
<p>The scalar value will be in energy <span class="xref doc">units</span>. The vector
values will typically also be in energy <span class="xref doc">units</span>, but see
the doc page for the pair style for details.</p>
</div>
<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="compute_pe.html"><span class="doc">compute pe</span></a>, <a class="reference internal" href="compute_bond.html"><span class="doc">compute bond</span></a></p>
</div>
<div class="section" id="default">
<h2>Default</h2>
<p>The default for <em>evalue</em> is <em>epair</em>.</p>
</div>
</div>
</div>
</div>
<footer>
<hr/>
<div role="contentinfo">
<p>
&copy; Copyright 2013 Sandia Corporation.
</p>
</div>
Built with <a href="http://sphinx-doc.org/">Sphinx</a> using a <a href="https://github.com/snide/sphinx_rtd_theme">theme</a> provided by <a href="https://readthedocs.org">Read the Docs</a>.
</footer>
</div>
</div>
</section>
</div>
<script type="text/javascript">
var DOCUMENTATION_OPTIONS = {
URL_ROOT:'./',
VERSION:'',
COLLAPSE_INDEX:false,
FILE_SUFFIX:'.html',
HAS_SOURCE: true
};
</script>
<script type="text/javascript" src="_static/jquery.js"></script>
<script type="text/javascript" src="_static/underscore.js"></script>
<script type="text/javascript" src="_static/doctools.js"></script>
<script type="text/javascript" src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script>
<script type="text/javascript" src="_static/sphinxcontrib-images/LightBox2/lightbox2/js/jquery-1.11.0.min.js"></script>
<script type="text/javascript" src="_static/sphinxcontrib-images/LightBox2/lightbox2/js/lightbox.min.js"></script>
<script type="text/javascript" src="_static/sphinxcontrib-images/LightBox2/lightbox2-customize/jquery-noconflict.js"></script>
<script type="text/javascript" src="_static/js/theme.js"></script>
<script type="text/javascript">
jQuery(function () {
SphinxRtdTheme.StickyNav.enable();
});
</script>
</body>
</html>
c4science · Help