Homec4science
Diffusion lammps (lammm-master) Browse

lammps/doc/html/pair_gauss.html
8d18bc0e6092lammm-master

Last Change
Raw File

pair_gauss.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>pair_style gauss 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>pair_style gauss 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="pair-style-gauss-command">
<span id="index-0"></span><h1>pair_style gauss command</h1>
</div>
<div class="section" id="pair-style-gauss-gpu-command">
<h1>pair_style gauss/gpu command</h1>
</div>
<div class="section" id="pair-style-gauss-omp-command">
<h1>pair_style gauss/omp command</h1>
</div>
<div class="section" id="pair-style-gauss-cut-command">
<h1>pair_style gauss/cut command</h1>
</div>
<div class="section" id="pair-style-gauss-cut-omp-command">
<h1>pair_style gauss/cut/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">gauss</span> <span class="n">cutoff</span>
<span class="n">pair_style</span> <span class="n">gauss</span><span class="o">/</span><span class="n">cut</span> <span class="n">cutoff</span>
</pre></div>
</div>
<ul class="simple">
<li>cutoff = global cutoff for Gauss 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">gauss</span> <span class="mf">12.0</span>
<span class="n">pair_coeff</span> <span class="o">*</span> <span class="o">*</span> <span class="mf">1.0</span> <span class="mf">0.9</span>
<span class="n">pair_coeff</span> <span class="mi">1</span> <span class="mi">4</span> <span class="mf">1.0</span> <span class="mf">0.9</span> <span class="mf">10.0</span>
</pre></div>
</div>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">pair_style</span> <span class="n">gauss</span><span class="o">/</span><span class="n">cut</span> <span class="mf">3.5</span>
<span class="n">pair_coeff</span> <span class="mi">1</span> <span class="mi">4</span> <span class="mf">0.2805</span> <span class="mf">1.45</span> <span class="mf">0.112</span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>Style <em>gauss</em> computes a tethering potential of the form</p>
<img alt="_images/pair_gauss.jpg" class="align-center" src="_images/pair_gauss.jpg" />
<p>between an atom and its corresponding tether site which will typically
be a frozen atom in the simulation. Rc is the cutoff.</p>
<p>The following coefficients must be defined for each pair of atom 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:</p>
<ul class="simple">
<li>A (energy units)</li>
<li>B (1/distance^2 units)</li>
<li>cutoff (distance units)</li>
</ul>
<p>The last coefficient is optional. If not specified, the global cutoff
is used.</p>
<p>Style <em>gauss/cut</em> computes a generalized Gaussian interaction potential
between pairs of particles:</p>
<img alt="_images/pair_gauss_cut.jpg" class="align-center" src="_images/pair_gauss_cut.jpg" />
<p>where H determines together with the standard deviation sigma_h the
peak height of the Gaussian function, and r_mh the peak position.
Examples of the use of the Gaussian potentials include implicit
solvent simulations of salt ions <a class="reference internal" href="#lenart"><span class="std std-ref">(Lenart)</span></a> and of surfactants
<a class="reference internal" href="#jusufi"><span class="std std-ref">(Jusufi)</span></a>. In these instances the Gaussian potential mimics
the hydration barrier between a pair of particles. The hydration
barrier is located at r_mh and has a width of sigma_h. The prefactor
determines the hight of the potential barrier.</p>
<p>The following coefficients must be defined for each pair of atom types
via the <a class="reference internal" href="pair_coeff.html"><span class="doc">pair_coeff</span></a> command as in the example 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:</p>
<ul class="simple">
<li>H (energy * distance units)</li>
<li>r_mh (distance units)</li>
<li>sigma_h (distance units)</li>
</ul>
<p>The global cutoff (r_c) specified in the pair_style command is used.</p>
<hr class="docutils" />
<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
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 USER-CUDA, 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 &#8220;-suffix command-line
switch7_Section_start.html#start_6 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>These pair styles do not support mixing. Thus, coefficients for all
I,J pairs must be specified explicitly.</p>
<p>The <em>gauss</em> style does not support the <a class="reference internal" href="pair_modify.html"><span class="doc">pair_modify</span></a>
shift option. There is no effect due to the Gaussian well beyond the
cutoff; hence reasonable cutoffs need to be specified.</p>
<p>The <em>gauss/cut</em> 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 Gauss-potential portion of the pair
interaction.</p>
<p>The <a class="reference internal" href="pair_modify.html"><span class="doc">pair_modify</span></a> table and tail options are not
relevant for these pair styles.</p>
<p>These pair styles write their 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>These pair styles 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. They do not support the
<em>inner</em>, <em>middle</em>, <em>outer</em> keywords.</p>
<p>The <em>gauss</em> pair style tallies an &#8220;occupancy&#8221; count of how many Gaussian-well
sites have an atom within the distance at which the force is a maximum
= sqrt(0.5/b). This quantity can be accessed via the <a class="reference internal" href="compute_pair.html"><span class="doc">compute pair</span></a> command as a vector of values of length 1.</p>
<p>To print this quantity to the log file (with a descriptive column
heading) the following commands could be included in an input script:</p>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">compute</span> <span class="n">gauss</span> <span class="nb">all</span> <span class="n">pair</span> <span class="n">gauss</span>
<span class="n">variable</span> <span class="n">occ</span> <span class="n">equal</span> <span class="n">c_gauss</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span>
<span class="n">thermo_style</span> <span class="n">custom</span> <span class="n">step</span> <span class="n">temp</span> <span class="n">epair</span> <span class="n">v_occ</span>
</pre></div>
</div>
</div>
<hr class="docutils" />
<div class="section" id="restrictions">
<h2>Restrictions</h2>
<p>The <em>gauss/cut</em> style is part of the &#8220;user-misc&#8221; 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</h2>
<p><a class="reference internal" href="pair_coeff.html"><span class="doc">pair_coeff</span></a>,
<a class="reference internal" href="pair_coul_diel.html"><span class="doc">pair_style coul/diel</span></a></p>
<p><strong>Default:</strong> none</p>
<p id="lenart"><strong>(Lenart)</strong> Lenart , Jusufi, and Panagiotopoulos, J Chem Phys, 126,
044509 (2007).</p>
<p id="jusufi"><strong>(Jusufi)</strong> Jusufi, Hynninen, and Panagiotopoulos, J Phys Chem B, 112,
13783 (2008).</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