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<a href="Manual.html" class="icon icon-home"> LAMMPS
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<div class="section" id="compute-temp-eff-command">
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<span id="index-0"></span><h1>compute temp/eff 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">eff</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/eff = style name of this compute command</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="mi">1</span> <span class="nb">all</span> <span class="n">temp</span><span class="o">/</span><span class="n">eff</span>
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<span class="n">compute</span> <span class="n">myTemp</span> <span class="n">mobile</span> <span class="n">temp</span><span class="o">/</span><span class="n">eff</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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nuclei and electrons in the <a class="reference internal" href="pair_eff.html"><span class="doc">electron force field</span></a>
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model. A compute of this style can be used by commands that compute a
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temperature, e.g. <a class="reference internal" href="thermo_modify.html"><span class="doc">thermo_modify</span></a>, <span class="xref doc">fix npt/eff</span>, etc.</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 for
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nuclei and sum of 1/2 (m v^2 + 3/4 m s^2) for electrons, where s
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includes the radial electron velocity contributions), dim = 2 or 3 =
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dimensionality of the simulation, N = number of atoms (only total
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number of nuclei in the eFF (see the <a class="reference internal" href="pair_style.html"><span class="doc">pair_eff</span></a>
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command) in the group, k = Boltzmann constant, and T = temperature.
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This expression is summed over all nuclear and electronic degrees of
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freedom, essentially by setting the kinetic contribution to the heat
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capacity to 3/2k (where only nuclei contribute). This subtlety is
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valid for temperatures well below the Fermi temperature, which for
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densities two to five times the density of liquid H2 ranges from
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86,000 to 170,000 K.</p>
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<div class="admonition note">
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<p class="first admonition-title">Note</p>
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<p class="last">For eFF models, in order to override the default temperature
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reported by LAMMPS in the thermodynamic quantities reported via the
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<a class="reference internal" href="thermo.html"><span class="doc">thermo</span></a> command, the user should apply a
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<a class="reference internal" href="thermo_modify.html"><span class="doc">thermo_modify</span></a> command, as shown in the following
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example:</p>
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</div>
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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">compute</span> <span class="n">effTemp</span> <span class="nb">all</span> <span class="n">temp</span><span class="o">/</span><span class="n">eff</span>
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<span class="n">thermo_style</span> <span class="n">custom</span> <span class="n">step</span> <span class="n">etotal</span> <span class="n">pe</span> <span class="n">ke</span> <span class="n">temp</span> <span class="n">press</span>
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<span class="n">thermo_modify</span> <span class="n">temp</span> <span class="n">effTemp</span>
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</pre></div>
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</div>
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<p>A 6-component kinetic energy tensor is also calculated by this compute
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for use in the computation of a pressure tensor. The formula for the
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components of the tensor is the same as the above formula, except that
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v^2 is replaced by vx * vy for the xy component, etc. For the eFF,
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again, the radial electronic velocities are also considered.</p>
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<p>The number of atoms contributing to the temperature is assumed to be
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constant for the duration of the run; use the <em>dynamic</em> option of the
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<a class="reference internal" href="compute_modify.html"><span class="doc">compute_modify</span></a> command if this is not the case.</p>
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<p>This compute subtracts out degrees-of-freedom due to fixes that
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constrain molecular motion, such as <a class="reference internal" href="fix_shake.html"><span class="doc">fix shake</span></a> and
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<a class="reference internal" href="fix_rigid.html"><span class="doc">fix rigid</span></a>. This means the temperature of groups of
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atoms that include these constraints will be computed correctly. If
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needed, the subtracted degrees-of-freedom can be altered using the
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<em>extra</em> option of the <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>The scalar value calculated by this compute is “intensive”, meaning it
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is independent of the number of atoms in the simulation. The vector
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values are “extensive”, meaning they scale with the number of atoms in
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the simulation.</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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<p>This compute is part of the USER-EFF 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 class="std std-ref">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</h2>
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<p><a class="reference internal" href="compute_temp_partial.html"><span class="doc">compute temp/partial</span></a>, <a class="reference internal" href="compute_temp_region.html"><span class="doc">compute temp/region</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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