2007-10-11 06:39:11 +08:00
2015-07-30 22:53:28 +08:00
<!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" >
2015-12-21 23:20:41 +08:00
< title > fix dt/reset command — LAMMPS documentation< / title >
2015-07-30 22:53:28 +08:00
2007-10-11 06:39:11 +08:00
2015-07-30 22:53:28 +08:00
2007-10-11 06:39:11 +08:00
2015-07-30 22:53:28 +08:00
2007-10-11 06:39:11 +08:00
2015-07-30 22:53:28 +08:00
2007-10-11 06:39:11 +08:00
2015-07-30 22:53:28 +08:00
2007-10-11 06:39:11 +08:00
2015-07-30 22:53:28 +08:00
< 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" / >
2015-12-21 23:20:41 +08:00
< link rel = "top" title = "LAMMPS documentation" href = "index.html" / >
2015-07-30 22:53:28 +08:00
< 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 & 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 & 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 >
< / 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 > » < / li >
< li > fix dt/reset 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-dt-reset-command" >
< span id = "index-0" > < / span > < h1 > fix dt/reset command< a class = "headerlink" href = "#fix-dt-reset-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 > fix ID group-ID dt/reset N Tmin Tmax Xmax keyword values ...
< / pre > < / div >
< / div >
< ul class = "simple" >
< li > ID, group-ID are documented in < a class = "reference internal" href = "fix.html" > < em > fix< / em > < / a > command< / li >
< li > dt/reset = style name of this fix command< / li >
< li > N = recompute dt every N timesteps< / li >
< li > Tmin = minimum dt allowed which can be NULL (time units)< / li >
< li > Tmax = maximum dt allowed which can be NULL (time units)< / li >
< li > Xmax = maximum distance for an atom to move in one timestep (distance units)< / li >
< li > zero or more keyword/value pairs may be appended< / li >
< li > keyword = < em > units< / em > < / li >
< / ul >
< pre class = "literal-block" >
< em > units< / em > value = < em > lattice< / em > or < em > box< / em >
2015-07-31 00:49:30 +08:00
lattice = Xmax is defined in lattice units
box = Xmax is defined in simulation box units
2015-07-30 22:53:28 +08:00
< / pre >
< / 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 > fix 5 all dt/reset 10 1.0e-5 0.01 0.1
fix 5 all dt/reset 10 0.01 2.0 0.2 units box
< / pre > < / div >
< / div >
< / div >
< div class = "section" id = "description" >
< h2 > Description< a class = "headerlink" href = "#description" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > Reset the timestep size every N steps during a run, so that no atom
2009-06-06 05:47:11 +08:00
moves further than Xmax, based on current atom velocities and forces.
This can be useful when starting from a configuration with overlapping
atoms, where forces will be large. Or it can be useful when running
an impact simulation where one or more high-energy atoms collide with
2015-07-30 22:53:28 +08:00
a solid, causing a damage cascade.< / p >
< p > This fix overrides the timestep size setting made by the
< a class = "reference internal" href = "timestep.html" > < em > timestep< / em > < / a > command. The new timestep size < em > dt< / em > is
computed in the following manner.< / p >
< p > For each atom, the timestep is computed that would cause it to
displace < em > Xmax< / em > on the next integration step, as a function of its
2009-06-06 05:47:11 +08:00
current velocity and force. Since performing this calculation exactly
would require the solution to a quartic equation, a cheaper estimate
2015-07-30 22:53:28 +08:00
is generated. The estimate is conservative in that the atom’ s
displacement is guaranteed not to exceed < em > Xmax< / em > , though it may be
smaller.< / p >
< p > Given this putative timestep for each atom, the minimum timestep value
across all atoms is computed. Then the < em > Tmin< / em > and < em > Tmax< / em > bounds are
2009-06-06 05:47:11 +08:00
applied, if specified. If one (or both) is specified as NULL, it is
2015-07-30 22:53:28 +08:00
not applied.< / p >
< p > When the < a class = "reference internal" href = "run_style.html" > < em > run style< / em > < / a > is < em > respa< / em > , this fix resets the
2007-10-11 06:39:11 +08:00
outer loop (largest) timestep, which is the same timestep that the
2015-07-30 22:53:28 +08:00
< a class = "reference internal" href = "timestep.html" > < em > timestep< / em > < / a > command sets.< / p >
< p > Note that the cumulative simulation time (in time units), which
2013-08-21 06:24:26 +08:00
accounts for changes in the timestep size as a simulation proceeds,
2015-07-30 22:53:28 +08:00
can be accessed by the < a class = "reference internal" href = "thermo_style.html" > < em > thermo_style time< / em > < / a > keyword.< / p >
< / div >
< div class = "section" id = "restart-fix-modify-output-run-start-stop-minimize-info" >
< h2 > Restart, fix_modify, output, run start/stop, minimize info< a class = "headerlink" href = "#restart-fix-modify-output-run-start-stop-minimize-info" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > No information about this fix is written to < a class = "reference internal" href = "restart.html" > < em > binary restart files< / em > < / a > . None of the < a class = "reference internal" href = "fix_modify.html" > < em > fix_modify< / em > < / a > options
are relevant to this fix.< / p >
< p > This fix computes a global scalar which can be accessed by various
< a class = "reference internal" href = "Section_howto.html#howto-15" > < span > output commands< / span > < / a > . The scalar stores
the last timestep on which the timestep was reset to a new value.< / p >
< p > The scalar value calculated by this fix is “ intensive” .< / p >
< p > No parameter of this fix can be used with the < em > start/stop< / em > keywords of
the < a class = "reference internal" href = "run.html" > < em > run< / em > < / a > command. This fix is not invoked during < a class = "reference internal" href = "minimize.html" > < em > energy minimization< / em > < / a > .< / p >
< / div >
< div class = "section" id = "restrictions" >
< h2 > Restrictions< a class = "headerlink" href = "#restrictions" title = "Permalink to this headline" > ¶< / a > < / h2 >
< blockquote >
< div > none< / div > < / blockquote >
< / 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 = "timestep.html" > < em > timestep< / em > < / a > < / p >
< / div >
< div class = "section" id = "default" >
< h2 > Default< a class = "headerlink" href = "#default" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > The option defaults is units = lattice.< / p >
< / div >
< / div >
< / div >
< / div >
< footer >
< hr / >
< div role = "contentinfo" >
< p >
2015-12-11 01:23:56 +08:00
© Copyright 2013 Sandia Corporation.
2015-07-30 22:53:28 +08:00
< / 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:'./',
2015-12-21 23:20:41 +08:00
VERSION:'',
2015-07-30 22:53:28 +08:00
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 >
