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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</h1>
<div class="section" id="syntax">
<h2>Syntax</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">compute_modify</span> <span class="n">compute</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>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>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">compute_modify</span> <span class="n">myTemp</span> <span class="n">extra</span> <span class="mi">0</span>
<span class="n">compute_modify</span> <span class="n">newtemp</span> <span class="n">dynamic</span> <span class="n">yes</span> <span class="n">extra</span> <span class="mi">600</span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description</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"><span class="doc">2d or 3d systems</span></a> which is a correction factor for an ensemble
of velocities with zero total linear momentum. For compute temp/partial,
if one or more velocity components are excluded, the value used for
<em>extra</em> is scaled accordingly. You can use a negative number for
the <em>extra</em> parameter if you need to add degrees-of-freedom.</p>
<blockquote>
<div>See the <a class="reference internal" href="compute_temp_asphere.html"><span class="doc">compute temp/asphere</span></a> command</div></blockquote>
<p>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"><span class="doc">fix pour</span></a> or <a class="reference internal" href="fix_deposit.html"><span class="doc">fix deposit</span></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"><span class="doc">fixes</span></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"><span class="doc">individual fixes</span></a> for details.</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="compute.html"><span class="doc">compute</span></a></p>
</div>
<div class="section" id="default">
<h2>Default</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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