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<div class="section" id="fix-drag-command">
<span id="index-0"></span><h1>fix drag command<a class="headerlink" href="#fix-drag-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>fix ID group-ID drag x y z fmag delta
</pre></div>
</div>
<ul class="simple">
<li>ID, group-ID are documented in <a class="reference internal" href="fix.html"><em>fix</em></a> command</li>
<li>drag = style name of this fix command</li>
<li>x,y,z = coord to drag atoms towards</li>
<li>fmag = magnitude of force to apply to each atom (force units)</li>
<li>delta = cutoff distance inside of which force is not applied (distance units)</li>
</ul>
</div>
<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>fix center small-molecule drag 0.0 10.0 0.0 5.0 2.0
</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>Apply a force to each atom in a group to drag it towards the point
(x,y,z). The magnitude of the force is specified by fmag. If an atom
is closer than a distance delta to the point, then the force is not
applied.</p>
<p>Any of the x,y,z values can be specified as NULL which means do not
include that dimension in the distance calculation or force
application.</p>
<p>This command can be used to steer one or more atoms to a new location
in the simulation.</p>
</div>
<div class="section" id="restart-fix-modify-output-run-start-stop-minimize-info">
<h2>Restart, fix_modify, output, run start/stop, minimize info<a class="headerlink" href="#restart-fix-modify-output-run-start-stop-minimize-info" title="Permalink to this headline"></a></h2>
<p>No information about this fix is written to <a class="reference internal" href="restart.html"><em>binary restart files</em></a>. None of the <a class="reference internal" href="fix_modify.html"><em>fix_modify</em></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>output commands</span></a>. This is the
total force on the group of atoms by the drag force. 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"><em>run</em></a> command. This fix is not invoked during <a class="reference internal" href="minimize.html"><em>energy minimization</em></a>.</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="fix_spring.html"><em>fix spring</em></a>, <a class="reference internal" href="fix_spring_self.html"><em>fix spring/self</em></a>,
<a class="reference internal" href="fix_spring_rg.html"><em>fix spring/rg</em></a>, <a class="reference internal" href="fix_smd.html"><em>fix smd</em></a></p>
<p><strong>Default:</strong> none</p>
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