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<div class="section" id="compute-improper-local-command">
<span id="index-0"></span><h1>compute improper/local 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">improper</span><span class="o">/</span><span class="n">local</span> <span class="n">value1</span> <span class="n">value2</span> <span class="o">...</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>improper/local = style name of this compute command</li>
<li>one or more values may be appended</li>
<li>value = <em>chi</em></li>
</ul>
<pre class="literal-block">
<em>chi</em> = tabulate improper angles
</pre>
</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">improper</span><span class="o">/</span><span class="n">local</span> <span class="n">chi</span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>Define a computation that calculates properties of individual improper
interactions. The number of datums generated, aggregated across all
processors, equals the number of impropers in the system, modified by
the group parameter as explained below.</p>
<p>The value <em>chi</em> is the improper angle, as defined in the doc pages for
the individual improper styles listed on
<a class="reference internal" href="improper_style.html"><span class="doc">improper_style</span></a> doc page.</p>
<p>The local data stored by this command is generated by looping over all
the atoms owned on a processor and their impropers. An improper will
only be included if all 4 atoms in the improper are in the specified
compute group.</p>
<p>Note that as atoms migrate from processor to processor, there will be
no consistent ordering of the entries within the local vector or array
from one timestep to the next. The only consistency that is
guaranteed is that the ordering on a particular timestep will be the
same for local vectors or arrays generated by other compute commands.
For example, improper output from the <a class="reference internal" href="compute_property_local.html"><span class="doc">compute property/local</span></a> command can be combined
with data from this command and output by the <a class="reference internal" href="dump.html"><span class="doc">dump local</span></a>
command in a consistent way.</p>
<p>Here is an example of how to do this:</p>
<pre class="literal-block">
compute 1 all property/local itype iatom1 iatom2 iatom3 iatom4
compute 2 all improper/local chi
dump 1 all local 1000 tmp.dump index c_1[1] c_1[2] c_1[3] c_1[4] c_1[5] c_2[1]
</pre>
<p><strong>Output info:</strong></p>
<p>This compute calculates a local vector or local array depending on the
number of keywords. The length of the vector or number of rows in the
array is the number of impropers. If a single keyword is specified, a
local vector is produced. If two or more keywords are specified, a
local array is produced where the number of columns = the number of
keywords. The vector or array can be accessed by any command that
uses local 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 output for <em>chi</em> will be in degrees.</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="dump.html"><span class="doc">dump local</span></a>, <a class="reference internal" href="compute_property_local.html"><span class="doc">compute property/local</span></a></p>
<p><strong>Default:</strong> none</p>
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