<spanid="index-0"></span><h1>fix nphug command<aclass="headerlink"href="#fix-nphug-command"title="Permalink to this headline">¶</a></h1>
</div>
<divclass="section"id="fix-nphug-omp-command">
<h1>fix nphug/omp command<aclass="headerlink"href="#fix-nphug-omp-command"title="Permalink to this headline">¶</a></h1>
<divclass="section"id="syntax">
<h2>Syntax<aclass="headerlink"href="#syntax"title="Permalink to this headline">¶</a></h2>
<divclass="highlight-python"><divclass="highlight"><pre>fix ID group-ID nphug keyword value ...
</pre></div>
</div>
<ulclass="simple">
<li>ID, group-ID are documented in <aclass="reference internal"href="fix.html"><em>fix</em></a> command</li>
</ul>
<preclass="literal-block">
one or more keyword value pairs may be appended
keyword = <em>temp</em> or <em>iso</em> or <em>aniso</em> or <em>tri</em> or <em>x</em> or <em>y</em> or <em>z</em> or <em>couple</em> or <em>tchain</em> or <em>pchain</em> or <em>mtk</em> or <em>tloop</em> or <em>ploop</em> or <em>nreset</em> or <em>drag</em> or <em>dilate</em> or <em>scaleyz</em> or <em>scalexz</em> or <em>scalexy</em>
other two cell dimensions are kept fixed (zero lateral strain).</p>
<p>This leads to the following additional restrictions on the keywords:</p>
<ulclass="simple">
<li>One and only one of the following keywords should be used: <em>iso</em>, <em>aniso</em>, <em>tri</em>, <em>x</em>, <em>y</em>, <em>z</em></li>
<li>The specified initial and final target pressures must be the same.</li>
<li>The keywords <em>xy</em>, <em>xz</em>, <em>yz</em> may not be used.</li>
<li>The only admissible value for the couple keyword is <em>xyz</em>, which has the same effect as keyword <em>iso</em></li>
<li>The <em>temp</em> keyword must be used to specify the time constant for kinetic energy relaxation, but initial and final target temperature values are ignored.</li>
</ul>
<p>Essentially, a Hugoniostat simulation is an NPT simulation in which the
user-specified target temperature is replaced with a time-dependent
target temperature Tt obtained from the following equation:</p>
<pclass="last">Unlike the <aclass="reference internal"href="fix_temp_berendsen.html"><em>fix temp/berendsen</em></a> command
which performs thermostatting but NO time integration, this fix
performs thermostatting/barostatting AND time integration. Thus you
should not use any other time integration fix, such as <aclass="reference internal"href="fix_nve.html"><em>fix nve</em></a> on atoms to which this fix is applied. Likewise,
this fix should not be used on atoms that have their temperature
controlled by another fix - e.g. by <aclass="reference internal"href="fix_nh.html"><em>fix langevin</em></a> or <aclass="reference internal"href="fix_temp_rescale.html"><em>fix temp/rescale</em></a> commands.</p>
<divclass="highlight-python"><divclass="highlight"><pre>compute fix-ID_temp all temp
compute fix-ID_press all pressure fix-ID_temp
</pre></div>
</div>
<p>See the <aclass="reference internal"href="compute_temp.html"><em>compute temp</em></a> and <aclass="reference internal"href="compute_pressure.html"><em>compute pressure</em></a> commands for details. Note that the
IDs of the new computes are the fix-ID + underscore + “temp” or fix_ID
+ underscore + “press”. The group for
the new computes is “all” since pressure is computed for the entire
system.</p>
<p>Note that these are NOT the computes used by thermodynamic output (see
the <aclass="reference internal"href="thermo_style.html"><em>thermo_style</em></a> command) with ID = <em>thermo_temp</em>
and <em>thermo_press</em>. This means you can change the attributes of this
fix’s temperature or pressure via the
<aclass="reference internal"href="compute_modify.html"><em>compute_modify</em></a> command or print this temperature
or pressure during thermodynamic output via the <aclass="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> or
<em>thermo_press</em> will have no effect on this fix.</p>
<hrclass="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
enabled if LAMMPS was built with those packages. See the <aclass="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 <aclass="reference internal"href="Section_start.html#start-7"><span>-suffix command-line switch</span></a> when you invoke LAMMPS, or you can
use the <aclass="reference internal"href="suffix.html"><em>suffix</em></a> command in your input script.</p>
<p>See <aclass="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>
<h2>Restart, fix_modify, output, run start/stop, minimize info<aclass="headerlink"href="#restart-fix-modify-output-run-start-stop-minimize-info"title="Permalink to this headline">¶</a></h2>
<p>This fix writes the values of E0, V0, and P0, as well as the
<p>These fixes compute a global scalar and a global vector of quantities,
which can be accessed by various <aclass="reference internal"href="Section_howto.html#howto-15"><span>output commands</span></a>. The scalar value calculated by
these fixes is “extensive”; the vector values are “intensive”.</p>
<p>The scalar is the cumulative energy change due to the fix.</p>
<p>The vector stores three quantities unique to this fix (Delta, Us, and up),
shock calculated from the RH conditions. They have units of distance/time.</p>
</div>
<divclass="section"id="restrictions">
<h2>Restrictions<aclass="headerlink"href="#restrictions"title="Permalink to this headline">¶</a></h2>
<p>This fix style is part of the SHOCK package. It is only enabled if
LAMMPS was built with that package. See the <aclass="reference internal"href="Section_start.html#start-3"><span>Making LAMMPS</span></a> section for more info.</p>
<p>All the usual restrictions for <aclass="reference internal"href="fix_nh.html"><em>fix_style npt</em></a> apply,
plus the additional ones mentioned above.</p>
</div>
<divclass="section"id="related-commands">
<h2>Related commands<aclass="headerlink"href="#related-commands"title="Permalink to this headline">¶</a></h2>
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