Homec4science
Diffusion lammps (master) Browse

lammps/doc/html/fix_modify.html
28a9a22aa614master

Last Change
Raw File

fix_modify.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>fix_modify 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>fix_modify 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="fix-modify-command">
<span id="index-0"></span><h1>fix_modify command</h1>
<div class="section" id="syntax">
<h2>Syntax</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">fix_modify</span> <span class="n">fix</span><span class="o">-</span><span class="n">ID</span> <span class="n">keyword</span> <span class="n">value</span> <span class="o">...</span>
</pre></div>
</div>
<ul class="simple">
<li>fix-ID = ID of the fix to modify</li>
<li>one or more keyword/value pairs may be appended</li>
<li>keyword = <em>temp</em> or <em>press</em> or <em>energy</em> or <em>respa</em></li>
</ul>
<pre class="literal-block">
<em>temp</em> value = compute ID that calculates a temperature
<em>press</em> value = compute ID that calculates a pressure
<em>energy</em> value = <em>yes</em> or <em>no</em>
<em>respa</em> value = <em>1</em> to <em>max respa level</em> or <em>0</em> (for outermost level)
</pre>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">fix_modify</span> <span class="mi">3</span> <span class="n">temp</span> <span class="n">myTemp</span> <span class="n">press</span> <span class="n">myPress</span>
<span class="n">fix_modify</span> <span class="mi">1</span> <span class="n">energy</span> <span class="n">yes</span>
<span class="n">fix_modify</span> <span class="n">tether</span> <span class="n">respa</span> <span class="mi">2</span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>Modify one or more parameters of a previously defined fix. Only
specific fix styles support specific parameters. See the doc pages
for individual fix commands for info on which ones support which
fix_modify parameters.</p>
<p>The <em>temp</em> keyword is used to determine how a fix computes
temperature. The specified compute ID must have been previously
defined by the user via the <a class="reference internal" href="compute.html"><span class="doc">compute</span></a> command and it must
be a style of compute that calculates a temperature. All fixes that
compute temperatures define their own compute by default, as described
in their documentation. Thus this option allows the user to override
the default method for computing T.</p>
<p>The <em>press</em> keyword is used to determine how a fix computes pressure.
The specified compute ID must have been previously defined by the user
via the <a class="reference internal" href="compute.html"><span class="doc">compute</span></a> command and it must be a style of
compute that calculates a pressure. All fixes that compute pressures
define their own compute by default, as described in their
documentation. Thus this option allows the user to override the
default method for computing P.</p>
<p>For fixes that calculate a contribution to the potential energy of the
system, the <em>energy</em> keyword will include that contribution in
thermodynamic output of potential energy. See the
<a class="reference internal" href="thermo_style.html"><span class="doc">thermo_style</span></a> command for info on how potential
energy is output. The contribution by itself can be printed by using
the keyword f_ID in the thermo_style custom command, where ID is the
fix-ID of the appropriate fix. Note that you must use this setting
for a fix if you are using it when performing an <a class="reference internal" href="minimize.html"><span class="doc">energy minimization</span></a> and if you want the energy and forces it
produces to be part of the optimization criteria.</p>
<p>For fixes that set or modify forces, it may be possible to select at
which <a class="reference internal" href="run_style.html"><span class="doc">r-RESPA</span></a> level the fix operates via the <em>respa</em>
keyword. The RESPA level at which the fix is active can be selected.
This is a number ranging from 1 to the number of levels. If the RESPA
level is larger than the current maximum, the outermost level will be
used, which is also the default setting. This default can be restored
using a value of <em>0</em> for the RESPA level. The affected fix has to be
enabled to support this feature; if not, <em>fix_modify</em> will report an
error. Active fixes with a custom RESPA level setting are reported
with their specified level at the beginning of a r-RESPA run.</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="fix.html"><span class="doc">fix</span></a>, <a class="reference internal" href="compute_temp.html"><span class="doc">compute temp</span></a>, <a class="reference internal" href="compute_pressure.html"><span class="doc">compute pressure</span></a>, <a class="reference internal" href="thermo_style.html"><span class="doc">thermo_style</span></a></p>
</div>
<div class="section" id="default">
<h2>Default</h2>
<p>The option defaults are temp = ID defined by fix, press = ID defined
by fix, energy = no, respa = 0.</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