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<div class="section" id="fix-nvt-sphere-command">
<span id="index-0"></span><h1>fix nvt/sphere command<a class="headerlink" href="#fix-nvt-sphere-command" title="Permalink to this headline">¶</a></h1>
</div>
<div class="section" id="fix-nvt-sphere-omp-command">
<h1>fix nvt/sphere/omp command<a class="headerlink" href="#fix-nvt-sphere-omp-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 nvt/sphere keyword value ...
</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>nvt/sphere = style name of this fix command</li>
<li>additional thermostat related keyword/value pairs from the <a class="reference internal" href="fix_nh.html"><em>fix nvt</em></a> command can be appended</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 1 all nvt/sphere temp 300.0 300.0 100.0
fix 1 all nvt/sphere temp 300.0 300.0 100.0 drag 0.2
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
<p>Perform constant NVT integration to update position, velocity, and
angular velocity each timestep for finite-size spherical particles in
the group using a Nose/Hoover temperature thermostat. V is volume; T
is temperature. This creates a system trajectory consistent with the
canonical ensemble.</p>
<p>This fix differs from the <a class="reference internal" href="fix_nh.html"><em>fix nvt</em></a> command, which
assumes point particles and only updates their position and velocity.</p>
<p>The thermostat is applied to both the translational and rotational
degrees of freedom for the spherical particles, assuming a compute is
used which calculates a temperature that includes the rotational
degrees of freedom (see below). The translational degrees of freedom
can also have a bias velocity removed from them before thermostatting
takes place; see the description below.</p>
<p>Additional parameters affecting the thermostat are specified by
keywords and values documented with the <a class="reference internal" href="fix_nh.html"><em>fix nvt</em></a>
command. See, for example, discussion of the <em>temp</em> and <em>drag</em>
keywords.</p>
<p>This fix computes a temperature each timestep. To do this, the fix
creates its own compute of style &#8220;temp/sphere&#8221;, as if this command
had been issued:</p>
<div class="highlight-python"><div class="highlight"><pre>compute fix-ID_temp group-ID temp/sphere
</pre></div>
</div>
<p>See the <a class="reference internal" href="compute_temp_sphere.html"><em>compute temp/sphere</em></a> command for
details. Note that the ID of the new compute is the fix-ID +
underscore + &#8220;temp&#8221;, and the group for the new compute is the same as
the fix group.</p>
<p>Note that this is NOT the compute used by thermodynamic output (see
the <a class="reference internal" href="thermo_style.html"><em>thermo_style</em></a> command) with ID = <em>thermo_temp</em>.
This means you can change the attributes of this fix&#8217;s temperature
(e.g. its degrees-of-freedom) via the
<a class="reference internal" href="compute_modify.html"><em>compute_modify</em></a> command or print this temperature
during thermodynamic output via the <a class="reference internal" href="thermo_style.html"><em>thermo_style custom</em></a> command using the appropriate compute-ID.
It also means that changing attributes of <em>thermo_temp</em> will have no
effect on this fix.</p>
<p>Like other fixes that perform thermostatting, this fix can be used
with <a class="reference internal" href="compute.html"><em>compute commands</em></a> that calculate a temperature
after removing a &#8220;bias&#8221; from the atom velocities. E.g. removing the
center-of-mass velocity from a group of atoms or only calculating
temperature on the x-component of velocity or only calculating
temperature for atoms in a geometric region. This is not done by
default, but only if the <a class="reference internal" href="fix_modify.html"><em>fix_modify</em></a> command is used
to assign a temperature compute to this fix that includes such a bias
term. See the doc pages for individual <a class="reference internal" href="compute.html"><em>compute commands</em></a> to determine which ones include a bias. In
this case, the thermostat works in the following manner: the current
temperature is calculated taking the bias into account, bias is
removed from each atom, thermostatting is performed on the remaining
thermal degrees of freedom, and the bias is added back in.</p>
<hr class="docutils" />
<p>Styles with a <em>cuda</em>, <em>gpu</em>, <em>intel</em>, <em>kk</em>, <em>omp</em>, or <em>opt</em> suffix are
functionally the same as the corresponding style without the suffix.
They have been optimized to run faster, depending on your available
hardware, as discussed in <a class="reference internal" href="Section_accelerate.html"><em>Section_accelerate</em></a>
of the manual. The accelerated styles take the same arguments and
should produce the same results, except for round-off and precision
issues.</p>
<p>These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
KOKKOS, USER-OMP and OPT packages, respectively. They are only
enabled if LAMMPS was built with those packages. See the <a class="reference internal" href="Section_start.html#start-3"><span>Making LAMMPS</span></a> section for more info.</p>
<p>You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the <a class="reference internal" href="Section_start.html#start-7"><span>-suffix command-line switch</span></a> when you invoke LAMMPS, or you can
use the <a class="reference internal" href="suffix.html"><em>suffix</em></a> command in your input script.</p>
<p>See <a class="reference internal" href="Section_accelerate.html"><em>Section_accelerate</em></a> of the manual for
more instructions on how to use the accelerated styles effectively.</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>This fix writes the state of the Nose/Hoover thermostat to <a class="reference internal" href="restart.html"><em>binary restart files</em></a>. See the <a class="reference internal" href="read_restart.html"><em>read_restart</em></a>
command for info on how to re-specify a fix in an input script that
reads a restart file, so that the operation of the fix continues in an
uninterrupted fashion.</p>
<p>The <a class="reference internal" href="fix_modify.html"><em>fix_modify</em></a> <em>temp</em> option is supported by this
fix. You can use it to assign a <a class="reference internal" href="compute.html"><em>compute</em></a> you have
defined to this fix which will be used in its thermostatting
procedure.</p>
<p>The <a class="reference internal" href="fix_modify.html"><em>fix_modify</em></a> <em>energy</em> option is supported by this
fix to add the energy change induced by Nose/Hoover thermostatting to
the system&#8217;s potential energy as part of <a class="reference internal" href="thermo_style.html"><em>thermodynamic output</em></a>.</p>
<p>This fix computes the same global scalar and global vector of
quantities as does the <a class="reference internal" href="fix_nh.html"><em>fix nvt</em></a> command.</p>
<p>This fix can ramp its target temperature over multiple runs, using the
<em>start</em> and <em>stop</em> keywords of the <a class="reference internal" href="run.html"><em>run</em></a> command. See the
<a class="reference internal" href="run.html"><em>run</em></a> command for details of how to do this.</p>
<p>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>
<p>This fix requires that atoms store torque and angular velocity (omega)
and a radius as defined by the <a class="reference internal" href="atom_style.html"><em>atom_style sphere</em></a>
command.</p>
<p>All particles in the group must be finite-size spheres. They cannot
be point particles.</p>
</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_nh.html"><em>fix nvt</em></a>, <a class="reference internal" href="fix_nve_sphere.html"><em>fix nve_sphere</em></a>, <a class="reference internal" href="fix_nvt_asphere.html"><em>fix nvt_asphere</em></a>, <a class="reference internal" href="fix_npt_sphere.html"><em>fix npt_sphere</em></a>, <a class="reference internal" href="fix_modify.html"><em>fix_modify</em></a></p>
<p><strong>Default:</strong> none</p>
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