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<div class="section" id="compute-ke-eff-command">
<span id="index-0"></span><h1>compute ke/eff command</h1>
<div class="section" id="syntax">
<h2>Syntax</h2>
<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">ke</span><span class="o">/</span><span class="n">eff</span>
</pre></div>
</div>
<ul class="simple">
<li>ID, group-ID are documented in <a class="reference internal" href="compute.html"><span class="doc">compute</span></a> command</li>
<li>ke/eff = style name of this compute 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">compute</span> <span class="mi">1</span> <span class="nb">all</span> <span class="n">ke</span><span class="o">/</span><span class="n">eff</span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>Define a computation that calculates the kinetic energy of motion of a
group of eFF particles (nuclei and electrons), as modeled with the
<a class="reference internal" href="pair_eff.html"><span class="doc">electronic force field</span></a>.</p>
<p>The kinetic energy for each nucleus is computed as 1/2 m v^2 and the
kinetic energy for each electron is computed as 1/2(me v^2 + 3/4 me
s^2), where m corresponds to the nuclear mass, me to the electron
mass, v to the translational velocity of each particle, and s to the
radial velocity of the electron, respectively.</p>
<p>There is a subtle difference between the quantity calculated by this
compute and the kinetic energy calculated by the <em>ke</em> or <em>etotal</em>
keyword used in thermodynamic output, as specified by the
<a class="reference internal" href="thermo_style.html"><span class="doc">thermo_style</span></a> command. For this compute, kinetic
energy is &#8220;translational&#8221; and &#8220;radial&#8221; (only for electrons) kinetic
energy, calculated by the simple formula above. For thermodynamic
output, the <em>ke</em> keyword infers kinetic energy from the temperature of
the system with 1/2 Kb T of energy for each degree of freedom. For
the eFF temperature computation via the <a class="reference internal" href="compute_temp_eff.html"><span class="doc">compute temp_eff</span></a> command, these are the same. But
different computes that calculate temperature can subtract out
different non-thermal components of velocity and/or include other
degrees of freedom.</p>
<p>IMPRORTANT NOTE: The temperature in eFF models should be monitored via
the <a class="reference internal" href="compute_temp_eff.html"><span class="doc">compute temp/eff</span></a> command, which can be
printed with thermodynamic output by using the
<a class="reference internal" href="thermo_modify.html"><span class="doc">thermo_modify</span></a> command, as shown in the following
example:</p>
<pre class="literal-block">
compute effTemp all temp/eff
thermo_style custom step etotal pe ke temp press
thermo_modify temp effTemp
</pre>
<p>See <a class="reference internal" href="compute_temp_eff.html"><span class="doc">compute temp/eff</span></a>.</p>
<p><strong>Output info:</strong></p>
<p>This compute calculates a global scalar (the KE). This value can be
used by any command that uses a global scalar value from a compute as
input. See <a class="reference internal" href="Section_howto.html#howto-15"><span class="std std-ref">Section_howto 15</span></a> for an
overview of LAMMPS output options.</p>
<p>The scalar value calculated by this compute is &#8220;extensive&#8221;. The
scalar value will be in energy <a class="reference internal" href="units.html"><span class="doc">units</span></a>.</p>
</div>
<div class="section" id="restrictions">
<h2>Restrictions</h2>
<p>This compute is part of the USER-EFF 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><strong>Related commands:</strong> none</p>
<p><strong>Default:</strong> none</p>
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