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<div class="lammps_version">Version: <b>19 Nov 2024</b></div>
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<li class="toctree-l1"><a class="reference internal" href="fixes.html">Fix Styles</a></li>
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<p><span class="math notranslate nohighlight">\(\renewcommand{\AA}{\text{Å}}\)</span></p>
<section id="improper-style-command">
<span id="index-0"></span><h1>improper_style command<a class="headerlink" href="#improper-style-command" title="Link to this heading"></a></h1>
<section id="syntax">
<h2>Syntax<a class="headerlink" href="#syntax" title="Link to this heading"></a></h2>
<div class="highlight-LAMMPS notranslate"><div class="highlight"><pre><span></span><span class="k">improper_style</span><span class="w"> </span><span class="n">style</span>
</pre></div>
</div>
<ul class="simple">
<li><p>style = <em>none</em> or <em>hybrid</em> or <em>class2</em> or <em>cvff</em> or <em>harmonic</em></p></li>
</ul>
</section>
<section id="examples">
<h2>Examples<a class="headerlink" href="#examples" title="Link to this heading"></a></h2>
<div class="highlight-LAMMPS notranslate"><div class="highlight"><pre><span></span><span class="k">improper_style</span><span class="w"> </span><span class="n">harmonic</span>
<span class="k">improper_style</span><span class="w"> </span><span class="n">cvff</span>
<span class="k">improper_style</span><span class="w"> </span><span class="n">hybrid</span><span class="w"> </span><span class="n">cvff</span><span class="w"> </span><span class="n">harmonic</span>
</pre></div>
</div>
</section>
<section id="description">
<h2>Description<a class="headerlink" href="#description" title="Link to this heading"></a></h2>
<p>Set the formula(s) LAMMPS uses to compute improper interactions
between quadruplets of atoms, which remain in force for the duration
of the simulation. The list of improper quadruplets is read in by a
<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> command
from a data or restart file. Note that the ordering of the 4 atoms in
an improper quadruplet determines the definition of the improper
angle used in the formula for each style. See the doc pages of
individual styles for details.</p>
<p>Hybrid models where impropers are computed using different improper
potentials can be setup using the <em>hybrid</em> improper style.</p>
<p>The coefficients associated with an improper style can be specified in
a data or restart file or via the <a class="reference internal" href="improper_coeff.html"><span class="doc">improper_coeff</span></a>
command.</p>
<p>All improper potentials store their coefficient data in binary restart
files which means improper_style and
<a class="reference internal" href="improper_coeff.html"><span class="doc">improper_coeff</span></a> commands do not need to be
re-specified in an input script that restarts a simulation. See the
<a class="reference internal" href="read_restart.html"><span class="doc">read_restart</span></a> command for details on how to do
this. The one exception is that improper_style <em>hybrid</em> only stores
the list of sub-styles in the restart file; improper coefficients need
to be re-specified.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>When both an improper and pair style is defined, the
<a class="reference internal" href="special_bonds.html"><span class="doc">special_bonds</span></a> command often needs to be used to
turn off (or weight) the pairwise interaction that would otherwise
exist between a group of 4 bonded atoms.</p>
</div>
<hr class="docutils" />
<p>Here is an alphabetic list of improper styles defined in LAMMPS.
Click on the style to display the formula it computes and coefficients
specified by the associated <a class="reference internal" href="improper_coeff.html"><span class="doc">improper_coeff</span></a>
command.</p>
<p>Click on the style to display the formula it computes, any additional
arguments specified in the improper_style command, and coefficients
specified by the associated <a class="reference internal" href="improper_coeff.html"><span class="doc">improper_coeff</span></a>
command.</p>
<p>There are also additional accelerated pair styles included in the
LAMMPS distribution for faster performance on CPUs, GPUs, and KNLs.
The individual style names on the <a class="reference internal" href="Commands_bond.html#improper"><span class="std std-ref">Commands improper</span></a> page are followed by one or
more of (g,i,k,o,t) to indicate which accelerated styles exist.</p>
<ul class="simple">
<li><p><a class="reference internal" href="improper_none.html"><span class="doc">none</span></a> - turn off improper interactions</p></li>
<li><p><a class="reference internal" href="improper_zero.html"><span class="doc">zero</span></a> - topology but no interactions</p></li>
<li><p><a class="reference internal" href="improper_hybrid.html"><span class="doc">hybrid</span></a> - define multiple styles of improper interactions</p></li>
<li><p><a class="reference internal" href="improper_amoeba.html"><span class="doc">amoeba</span></a> - AMOEBA out-of-plane improper</p></li>
<li><p><a class="reference internal" href="improper_class2.html"><span class="doc">class2</span></a> - COMPASS (class 2) improper</p></li>
<li><p><a class="reference internal" href="improper_cossq.html"><span class="doc">cossq</span></a> - improper with a cosine squared term</p></li>
<li><p><a class="reference internal" href="improper_cvff.html"><span class="doc">cvff</span></a> - CVFF improper</p></li>
<li><p><a class="reference internal" href="improper_distance.html"><span class="doc">distance</span></a> - improper based on distance between atom planes</p></li>
<li><p><a class="reference internal" href="improper_distharm.html"><span class="doc">distharm</span></a> - improper that is harmonic in the out-of-plane distance</p></li>
<li><p><a class="reference internal" href="improper_fourier.html"><span class="doc">fourier</span></a> - improper with multiple cosine terms</p></li>
<li><p><a class="reference internal" href="improper_harmonic.html"><span class="doc">harmonic</span></a> - harmonic improper</p></li>
<li><p><a class="reference internal" href="improper_inversion_harmonic.html"><span class="doc">inversion/harmonic</span></a> - harmonic improper with Wilson-Decius out-of-plane definition</p></li>
<li><p><a class="reference internal" href="improper_ring.html"><span class="doc">ring</span></a> - improper which prevents planar conformations</p></li>
<li><p><a class="reference internal" href="improper_umbrella.html"><span class="doc">umbrella</span></a> - DREIDING improper</p></li>
<li><p><a class="reference internal" href="improper_sqdistharm.html"><span class="doc">sqdistharm</span></a> - improper that is harmonic in the square of the out-of-plane distance</p></li>
</ul>
</section>
<hr class="docutils" />
<section id="restrictions">
<h2>Restrictions<a class="headerlink" href="#restrictions" title="Link to this heading"></a></h2>
<p>Improper styles can only be set for atom_style choices that allow
impropers to be defined.</p>
<p>Most improper styles are part of the MOLECULE package. They are only
enabled if LAMMPS was built with that package. See the <a class="reference internal" href="Build_package.html"><span class="doc">Build package</span></a> page for more info. The doc pages for
individual improper potentials tell if it is part of a package.</p>
</section>
<section id="related-commands">
<h2>Related commands<a class="headerlink" href="#related-commands" title="Link to this heading"></a></h2>
<p><a class="reference internal" href="improper_coeff.html"><span class="doc">improper_coeff</span></a></p>
</section>
<section id="default">
<h2>Default<a class="headerlink" href="#default" title="Link to this heading"></a></h2>
<div class="highlight-LAMMPS notranslate"><div class="highlight"><pre><span></span><span class="k">improper_style</span><span class="w"> </span><span class="n">none</span>
</pre></div>
</div>
</section>
</section>
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