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<li class="toctree-l1"><a class="reference internal" href="Section_intro.html">1. Introduction</a></li>
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<li class="toctree-l1"><a class="reference internal" href="Section_commands.html">3. Commands</a></li>
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<li class="toctree-l1"><a class="reference internal" href="Section_accelerate.html">5. Accelerating LAMMPS performance</a></li>
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<li class="toctree-l1"><a class="reference internal" href="Section_python.html">11. Python interface to LAMMPS</a></li>
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<li class="toctree-l1"><a class="reference internal" href="Section_errors.html">12. Errors</a></li>
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<li>compute temp/region command</li>
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<div class="section" id="compute-temp-region-command">
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<span id="index-0"></span><h1>compute temp/region command</h1>
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<div class="section" id="syntax">
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<h2>Syntax</h2>
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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">compute</span> <span class="n">ID</span> <span class="n">group</span><span class="o">-</span><span class="n">ID</span> <span class="n">temp</span><span class="o">/</span><span class="n">region</span> <span class="n">region</span><span class="o">-</span><span class="n">ID</span>
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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="compute.html"><span class="doc">compute</span></a> command</li>
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<li>temp/region = style name of this compute command</li>
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<li>region-ID = ID of region to use for choosing atoms</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</h2>
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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">compute</span> <span class="n">mine</span> <span class="n">flow</span> <span class="n">temp</span><span class="o">/</span><span class="n">region</span> <span class="n">boundary</span>
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</pre></div>
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</div>
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</div>
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<div class="section" id="description">
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<h2>Description</h2>
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<p>Define a computation that calculates the temperature of a group of
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atoms in a geometric region. This can be useful for thermostatting
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one portion of the simulation box. E.g. a McDLT simulation where one
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side is cooled, and the other side is heated. A compute of this style
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can be used by any command that computes a temperature,
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e.g. <a class="reference internal" href="thermo_modify.html"><span class="doc">thermo_modify</span></a>, <a class="reference internal" href="fix_temp_rescale.html"><span class="doc">fix temp/rescale</span></a>, etc.</p>
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<p>Note that a <em>region</em>-style temperature can be used to thermostat with
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<a class="reference internal" href="fix_temp_rescale.html"><span class="doc">fix temp/rescale</span></a> or <a class="reference internal" href="fix_langevin.html"><span class="doc">fix langevin</span></a>, but should probably not be used with
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Nose/Hoover style fixes (<a class="reference internal" href="fix_nh.html"><span class="doc">fix nvt</span></a>, <a class="reference internal" href="fix_nh.html"><span class="doc">fix npt</span></a>, or <a class="reference internal" href="fix_nh.html"><span class="doc">fix nph</span></a>), if the
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degrees-of-freedom included in the computed T varies with time.</p>
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<p>The temperature is calculated by the formula KE = dim/2 N k T, where
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KE = total kinetic energy of the group of atoms (sum of 1/2 m v^2),
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dim = 2 or 3 = dimensionality of the simulation, N = number of atoms
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in both the group and region, k = Boltzmann constant, and T =
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temperature.</p>
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<p>A kinetic energy tensor, stored as a 6-element vector, is also
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calculated by this compute for use in the computation of a pressure
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tensor. The formula for the components of the tensor is the same as
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the above formula, except that v^2 is replaced by vx*vy for the xy
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component, etc. The 6 components of the vector are ordered xx, yy,
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zz, xy, xz, yz.</p>
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<p>The number of atoms contributing to the temperature is calculated each
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time the temperature is evaluated since it is assumed atoms can
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enter/leave the region. Thus there is no need to use the <em>dynamic</em>
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option of the <a class="reference internal" href="compute_modify.html"><span class="doc">compute_modify</span></a> command for this
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compute style.</p>
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<p>The removal of atoms outside the region by this fix is essentially
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computing the temperature after a “bias” has been removed, which in
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this case is the velocity of any atoms outside the region. If this
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compute is used with a fix command that performs thermostatting then
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this bias will be subtracted from each atom, thermostatting of the
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remaining thermal velocity will be performed, and the bias will be
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added back in. Thermostatting fixes that work in this way include
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<a class="reference internal" href="fix_nh.html"><span class="doc">fix nvt</span></a>, <a class="reference internal" href="fix_temp_rescale.html"><span class="doc">fix temp/rescale</span></a>, <a class="reference internal" href="fix_temp_berendsen.html"><span class="doc">fix temp/berendsen</span></a>, and <a class="reference internal" href="fix_langevin.html"><span class="doc">fix langevin</span></a>. This means that when this compute
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is used to calculate the temperature for any of the thermostatting
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fixes via the <a class="reference internal" href="fix_modify.html"><span class="doc">fix modify temp</span></a> command, the thermostat
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will operate only on atoms that are currently in the geometric
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region.</p>
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<p>Unlike other compute styles that calculate temperature, this compute
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does not subtract out degrees-of-freedom due to fixes that constrain
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motion, such as <a class="reference internal" href="fix_shake.html"><span class="doc">fix shake</span></a> and <a class="reference internal" href="fix_rigid.html"><span class="doc">fix rigid</span></a>. This is because those degrees of freedom
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(e.g. a constrained bond) could apply to sets of atoms that straddle
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the region boundary, and hence the concept is somewhat ill-defined.
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If needed the number of subtracted degrees-of-freedom can be set
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explicitly using the <em>extra</em> option of the
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<a class="reference internal" href="compute_modify.html"><span class="doc">compute_modify</span></a> command.</p>
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<p>See <a class="reference internal" href="Section_howto.html#howto-16"><span class="std std-ref">this howto section</span></a> of the manual for
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a discussion of different ways to compute temperature and perform
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thermostatting.</p>
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<p><strong>Output info:</strong></p>
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<p>This compute calculates a global scalar (the temperature) and a global
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vector of length 6 (KE tensor), which can be accessed by indices 1-6.
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These values can be used by any command that uses global scalar or
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vector values from a compute as input. See <a class="reference internal" href="Section_howto.html#howto-15"><span class="std std-ref">this section</span></a> for an overview of LAMMPS output
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options.</p>
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<p>The scalar value calculated by this compute is “intensive”. The
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vector values are “extensive”.</p>
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<p>The scalar value will be in temperature <a class="reference internal" href="units.html"><span class="doc">units</span></a>. The
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vector values will be in energy <a class="reference internal" href="units.html"><span class="doc">units</span></a>.</p>
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</div>
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<div class="section" id="restrictions">
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<h2>Restrictions</h2>
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<blockquote>
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<div>none</div></blockquote>
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</div>
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<div class="section" id="related-commands">
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<h2>Related commands</h2>
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<p><a class="reference internal" href="compute_temp.html"><span class="doc">compute temp</span></a>, <a class="reference internal" href="compute_pressure.html"><span class="doc">compute pressure</span></a></p>
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<p><strong>Default:</strong> none</p>
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