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<li class="toctree-l1"><a class="reference internal" href="Section_modify.html">10. Modifying &amp; extending LAMMPS</a></li>
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<div class="section" id="compute-modify-command">
<span id="index-0"></span><h1>compute_modify command<a class="headerlink" href="#compute-modify-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>compute_modify compute-ID keyword value ...
</pre></div>
</div>
<ul class="simple">
<li>compute-ID = ID of the compute to modify</li>
<li>one or more keyword/value pairs may be listed</li>
<li>keyword = <em>extra</em> or <em>dynamic</em></li>
</ul>
<pre class="literal-block">
<em>extra</em> value = N
N = # of extra degrees of freedom to subtract
<em>dynamic</em> value = <em>yes</em> or <em>no</em>
yes/no = do or do not recompute the number of atoms contributing to the temperature
<em>thermo</em> value = <em>yes</em> or <em>no</em>
yes/no = do or do not add contributions from fixes to the potential energy
</pre>
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<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>compute_modify myTemp extra 0
compute_modify newtemp dynamic yes extra 600
</pre></div>
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</div>
<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline"></a></h2>
<p>Modify one or more parameters of a previously defined compute. Not
all compute styles support all parameters.</p>
<p>The <em>extra</em> keyword refers to how many degrees-of-freedom are
subtracted (typically from 3N) as a normalizing factor in a
temperature computation. Only computes that compute a temperature use
this option. The default is 2 or 3 for <a class="reference internal" href="dimension.html"><em>2d or 3d systems</em></a> which is a correction factor for an ensemble
of velocities with zero total linear momentum. You can use a negative
number for the <em>extra</em> parameter if you need to add
degrees-of-freedom. See the <a class="reference internal" href="compute_temp_asphere.html"><em>compute temp/asphere</em></a> command for an example.</p>
<p>The <em>dynamic</em> keyword determines whether the number of atoms N in the
compute group is re-computed each time a temperature is computed.
Only compute styles that compute a temperature use this option. By
default, N is assumed to be constant. If you are adding atoms to the
system (see the <a class="reference internal" href="fix_pour.html"><em>fix pour</em></a> or <a class="reference internal" href="fix_deposit.html"><em>fix deposit</em></a> commands) or expect atoms to be lost
(e.g. due to evaporation), then this option should be used to insure
the temperature is correctly normalized.</p>
<p>The <em>thermo</em> keyword determines whether the potential energy
contribution calculated by some <a class="reference internal" href="fix.html"><em>fixes</em></a> is added to the
potential energy calculated by the compute. Currently, only the
compute of style <em>pe</em> uses this option. See the doc pages for
<a class="reference internal" href="fix.html"><em>individual fixes</em></a> for details.</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="compute.html"><em>compute</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 are extra = 2 or 3 for 2d or 3d systems and
dynamic = no. Thermo is <em>yes</em> if the compute of style <em>pe</em> was
defined with no extra keywords; otherwise it is <em>no</em>.</p>
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