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<div class="section" id="fix-addtorque-command">
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<span id="index-0"></span><h1>fix addtorque command<a class="headerlink" href="#fix-addtorque-command" title="Permalink to this headline">¶</a></h1>
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<div class="section" id="syntax">
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<h2>Syntax<a class="headerlink" href="#syntax" title="Permalink to this headline">¶</a></h2>
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<div class="highlight-python"><div class="highlight"><pre>fix ID group-ID addtorque Tx Ty Tz
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</pre></div>
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</div>
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<ul class="simple">
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<li>ID, group-ID are documented in <a class="reference internal" href="fix.html"><em>fix</em></a> command</li>
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<li>addtorque = style name of this fix command</li>
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<li>Tx,Ty,Tz = torque component values (torque units)</li>
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<li>any of Tx,Ty,Tz can be a variable (see below)</li>
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</ul>
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</div>
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<div class="section" id="examples">
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<h2>Examples<a class="headerlink" href="#examples" title="Permalink to this headline">¶</a></h2>
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<div class="highlight-python"><div class="highlight"><pre>fix kick bead addtorque 2.0 3.0 5.0
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fix kick bead addtorque 0.0 0.0 v_oscillate
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</pre></div>
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</div>
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<div class="section" id="description">
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<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
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<p>Add a set of forces to each atom in
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the group such that:</p>
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<ul class="simple">
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<li>the components of the total torque applied on the group (around its
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center of mass) are Tx,Ty,Tz</li>
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<li>the group would move as a rigid body in the absence of other
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forces.</li>
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</ul>
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<p>This command can be used to drive a group of atoms into rotation.</p>
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<p>Any of the 3 quantities defining the torque components can be specified
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as an equal-style <a class="reference internal" href="variable.html"><em>variable</em></a>, namely <em>Tx</em>,
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<em>Ty</em>, <em>Tz</em>. If the value is a variable, it should be specified as
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v_name, where name is the variable name. In this case, the variable
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will be evaluated each timestep, and its value used to determine the
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torque component.</p>
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<p>Equal-style variables can specify formulas with various mathematical
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functions, and include <a class="reference internal" href="thermo_style.html"><em>thermo_style</em></a> command
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keywords for the simulation box parameters and timestep and elapsed
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time. Thus it is easy to specify a time-dependent torque.</p>
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</div>
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<hr class="docutils" />
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<div class="section" id="restart-fix-modify-output-run-start-stop-minimize-info">
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<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>
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<p>No information about this fix is written to <a class="reference internal" href="restart.html"><em>binary restart files</em></a>.</p>
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<p>The <a class="reference internal" href="fix_modify.html"><em>fix_modify</em></a> <em>energy</em> option is supported by this
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fix to add the potential “energy” inferred by the added forces to the
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system’s potential energy as part of <a class="reference internal" href="thermo_style.html"><em>thermodynamic output</em></a>. This is a fictitious quantity but is
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needed so that the <a class="reference internal" href="minimize.html"><em>minimize</em></a> command can include the
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forces added by this fix in a consistent manner. I.e. there is a
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decrease in potential energy when atoms move in the direction of the
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added forces.</p>
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<p>This fix computes a global scalar and a global 3-vector, which can be
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accessed by various <a class="reference internal" href="Section_howto.html#howto-15"><span>output commands</span></a>.
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The scalar is the potential energy discussed above. The vector is the
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total torque on the group of atoms before the forces on individual
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atoms are changed by the fix. The scalar and vector values calculated
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by this fix are “extensive”.</p>
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<p>No parameter of this fix can be used with the <em>start/stop</em> keywords of
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the <a class="reference internal" href="run.html"><em>run</em></a> command.</p>
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<p>The forces due to this fix are imposed during an energy minimization,
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invoked by the <a class="reference internal" href="minimize.html"><em>minimize</em></a> command. You should not
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specify force components with a variable that has time-dependence for
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use with a minimizer, since the minimizer increments the timestep as
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the iteration count during the minimization.</p>
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</div>
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<div class="section" id="restrictions">
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<h2>Restrictions<a class="headerlink" href="#restrictions" title="Permalink to this headline">¶</a></h2>
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<p>This fix is part of the USER-MISC package. It is only enabled if
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LAMMPS was built with that package. See the <a class="reference internal" href="Section_start.html#start-3"><span>Making LAMMPS</span></a> section for more info.</p>
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</div>
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<div class="section" id="related-commands">
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<h2>Related commands<a class="headerlink" href="#related-commands" title="Permalink to this headline">¶</a></h2>
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<p><a class="reference internal" href="fix_addforce.html"><em>fix addforce</em></a></p>
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<p><strong>Default:</strong> none</p>
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