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<div class="section" id="fix-freeze-command">
<span id="index-0"></span><h1>fix freeze command</h1>
<div class="section" id="syntax">
<h2>Syntax</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">fix</span> <span class="n">ID</span> <span class="n">group</span><span class="o">-</span><span class="n">ID</span> <span class="n">freeze</span>
</pre></div>
</div>
<ul class="simple">
<li>ID, group-ID are documented in <a class="reference internal" href="fix.html"><span class="doc">fix</span></a> command</li>
<li>freeze = style name of this fix command</li>
</ul>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">fix</span> <span class="mi">2</span> <span class="n">bottom</span> <span class="n">freeze</span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>Zero out the force and torque on a granular particle. This is useful
for preventing certain particles from moving in a simulation. The
<a class="reference internal" href="pair_gran.html"><span class="doc">granular pair styles</span></a> also detect if this fix has been
defined and compute interactions between frozen and non-frozen
particles appropriately, as if the frozen particle has infinite mass.
A similar functionality for normal (point) particles can be obtained
using <a class="reference internal" href="fix_setforce.html"><span class="doc">fix setforce</span></a>.</p>
<hr class="docutils" />
<p>Styles with a uffix are functionally the same as the corresponding
style without the suffix. They have been optimized to run faster,
depending on your available hardware, as discussed in
<a class="reference internal" href="Section_accelerate.html"><span class="doc">Section_accelerate</span></a> of the manual. The
accelerated styles take the same arguments and should produce the same
results, except for round-off and precision issues.</p>
<p>These accelerated styles are part of the ackage. They are only
enabled if LAMMPS was built with that package. See the <a class="reference internal" href="Section_start.html#start-3"><span class="std std-ref">Making LAMMPS</span></a> section for more info.</p>
<p>You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the <a class="reference internal" href="Section_start.html#start-7"><span class="std std-ref">-suffix command-line switch</span></a> when you invoke LAMMPS, or you can
use the <a class="reference internal" href="suffix.html"><span class="doc">suffix</span></a> command in your input script.</p>
<p>See <a class="reference internal" href="Section_accelerate.html"><span class="doc">Section_accelerate</span></a> of the manual for
more instructions on how to use the accelerated styles effectively.</p>
</div>
<hr class="docutils" />
<div class="section" id="restart-fix-modify-output-run-start-stop-minimize-info">
<h2>Restart, fix_modify, output, run start/stop, minimize info</h2>
<p>No information about this fix is written to <a class="reference internal" href="restart.html"><span class="doc">binary restart files</span></a>. None of the <a class="reference internal" href="fix_modify.html"><span class="doc">fix_modify</span></a> options
are relevant to this fix.</p>
<p>This fix computes a global 3-vector of forces, which can be accessed
by various <a class="reference internal" href="Section_howto.html#howto-15"><span class="std std-ref">output commands</span></a>. This is the
total force on the group of atoms before the forces on individual
atoms are changed by the fix. The vector values calculated by this
fix are &#8220;extensive&#8221;.</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"><span class="doc">run</span></a> command. This fix is not invoked during <a class="reference internal" href="minimize.html"><span class="doc">energy minimization</span></a>.</p>
</div>
<div class="section" id="restrictions">
<h2>Restrictions</h2>
<p>This fix is part of the GRANULAR package. It is only enabled if
LAMMPS was built with that package. See the <a class="reference internal" href="Section_start.html#start-3"><span class="std std-ref">Making LAMMPS</span></a> section for more info.</p>
<p>There can only be a single freeze fix defined. This is because other
the <a class="reference internal" href="pair_gran.html"><span class="doc">granular pair styles</span></a> treat frozen particles
differently and need to be able to reference a single group to which
this fix is applied.</p>
</div>
<div class="section" id="related-commands">
<h2>Related commands</h2>
<p><a class="reference internal" href="atom_style.html"><span class="doc">atom_style sphere</span></a>, <a class="reference internal" href="fix_setforce.html"><span class="doc">fix setforce</span></a></p>
<p><strong>Default:</strong> none</p>
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