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4
doc/Section_commands.txt
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@ -521,9 +521,11 @@ g = GPU, i = USER-INTEL, k = KOKKOS, o = USER-OMP, t = OPT.
"nph (ko)"_fix_nh.html,
"nphug (o)"_fix_nphug.html,
"nph/asphere (o)"_fix_nph_asphere.html,
"nph/body"_fix_nph_body.html,
"nph/sphere (o)"_fix_nph_sphere.html,
"npt (ckio)"_fix_nh.html,
"npt/asphere (o)"_fix_npt_asphere.html,
"npt/body"_fix_npt_body.html,
"npt/sphere (o)"_fix_npt_sphere.html,
"nve (ckio)"_fix_nve.html,
"nve/asphere (i)"_fix_nve_asphere.html,
@ -536,6 +538,7 @@ g = GPU, i = USER-INTEL, k = KOKKOS, o = USER-OMP, t = OPT.
"nve/tri"_fix_nve_tri.html,
"nvt (ciko)"_fix_nh.html,
"nvt/asphere (o)"_fix_nvt_asphere.html,
"nvt/body"_fix_nvt_body.html,
"nvt/sllod (io)"_fix_nvt_sllod.html,
"nvt/sphere (o)"_fix_nvt_sphere.html,
"oneway"_fix_oneway.html,
@ -719,6 +722,7 @@ KOKKOS, o = USER-OMP, t = OPT.
"stress/atom"_compute_stress_atom.html,
"temp (ck)"_compute_temp.html,
"temp/asphere"_compute_temp_asphere.html,
"temp/body"_compute_temp_body.html,
"temp/chunk"_compute_temp_chunk.html,
"temp/com"_compute_temp_com.html,
"temp/deform"_compute_temp_deform.html,

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<div class="section" id="fix-nph-body-command">
<span id="index-0"></span><h1>fix nph/body command<a class="headerlink" href="#fix-nph-body-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 nph/body args 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>nph/body = style name of this fix command</li>
<li>additional barostat related keyword/value pairs from the <a class="reference internal" href="fix_nh.html"><em>fix nph</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 nph/body iso 0.0 0.0 1000.0
fix 2 all nph/body x 5.0 5.0 1000.0
fix 2 all nph/body x 5.0 5.0 1000.0 drag 0.2
fix 2 water nph/body aniso 0.0 0.0 1000.0 dilate partial
</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 NPH integration to update position, velocity,
orientation, and angular velocity each timestep for body
particles in the group using a Nose/Hoover pressure
barostat. P is pressure; H is enthalpy. This creates a system
trajectory consistent with the isenthalpic ensemble.</p>
<p>This fix differs from the <a class="reference internal" href="fix_nh.html"><em>fix nph</em></a> command, which assumes
point particles and only updates their position and velocity.</p>
<p>Additional parameters affecting the barostat are specified by keywords
and values documented with the <a class="reference internal" href="fix_nh.html"><em>fix nph</em></a> command. See,
for example, discussion of the <em>aniso</em>, and <em>dilate</em> keywords.</p>
<p>The particles in the fix group are the only ones whose velocities and
positions are updated by the velocity/position update portion of the
NPH integration.</p>
<p>Regardless of what particles are in the fix group, a global pressure is
computed for all particles. Similarly, when the size of the simulation
box is changed, all particles are re-scaled to new positions, unless the
keyword <em>dilate</em> is specified with a value of <em>partial</em>, in which case
only the particles in the fix group are re-scaled. The latter can be
useful for leaving the coordinates of particles in a solid substrate
unchanged and controlling the pressure of a surrounding fluid.</p>
<hr class="docutils" />
<p>This fix computes a temperature and pressure each timestep. To do
this, the fix creates its own computes of style &#8220;temp/body&#8221; and
&#8220;pressure&#8221;, as if these commands had been issued:</p>
<div class="highlight-python"><div class="highlight"><pre>compute fix-ID_temp all temp/body
compute fix-ID_press all pressure fix-ID_temp
</pre></div>
</div>
<p>See the <a class="reference internal" href="compute_temp_body.html"><em>compute temp/body</em></a> and <a class="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 + &#8220;temp&#8221; or fix_ID
+ underscore + &#8220;press&#8221;, and the group for the new computes is &#8220;all&#8221;
since pressure is computed for the entire system.</p>
<p>Note that these are NOT the computes 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>
and <em>thermo_press</em>. This means you can change the attributes of this
fix&#8217;s temperature or pressure via the
<a class="reference internal" href="compute_modify.html"><em>compute_modify</em></a> command or print this temperature
or pressure 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> or
<em>thermo_press</em> will have no effect on this fix.</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 barostat 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> and <em>press</em> options are
supported by this fix. You can use them 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 or barostatting procedure. If you do this, note
that the kinetic energy derived from the compute temperature should be
consistent with the virial term computed using all atoms for the
pressure. LAMMPS will warn you if you choose to compute temperature
on a subset of atoms.</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 barostatting 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 nph</em></a> command.</p>
<p>This fix can ramp its target pressure 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 is part of the BODY 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>Making LAMMPS</span></a> section for more info.</p>
<p>This fix requires that atoms store torque and angular momementum and a
quaternion as defined by the <a class="reference internal" href="atom_style.html"><em>atom_style body</em></a>
command.</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 nph</em></a>, <a class="reference internal" href="fix_nve_body.html"><em>fix nve_body</em></a>, <a class="reference internal" href="fix_nvt_body.html"><em>fix nvt_body</em></a>, <a class="reference internal" href="fix_npt_body.html"><em>fix npt_body</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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148
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@ -0,0 +1,148 @@
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)
:line
fix nph/body command :h3
[Syntax:]
fix ID group-ID nph/body args keyword value ... :pre
ID, group-ID are documented in "fix"_fix.html command
nph/body = style name of this fix command
additional barostat related keyword/value pairs from the "fix nph"_fix_nh.html command can be appended :ul
[Examples:]
fix 1 all nph/body iso 0.0 0.0 1000.0
fix 2 all nph/body x 5.0 5.0 1000.0
fix 2 all nph/body x 5.0 5.0 1000.0 drag 0.2
fix 2 water nph/body aniso 0.0 0.0 1000.0 dilate partial :pre
[Description:]
Perform constant NPH integration to update position, velocity,
orientation, and angular velocity each timestep for body
particles in the group using a Nose/Hoover pressure
barostat. P is pressure; H is enthalpy. This creates a system
trajectory consistent with the isenthalpic ensemble.
This fix differs from the "fix nph"_fix_nh.html command, which assumes
point particles and only updates their position and velocity.
Additional parameters affecting the barostat are specified by keywords
and values documented with the "fix nph"_fix_nh.html command. See,
for example, discussion of the {aniso}, and {dilate} keywords.
The particles in the fix group are the only ones whose velocities and
positions are updated by the velocity/position update portion of the
NPH integration.
Regardless of what particles are in the fix group, a global pressure is
computed for all particles. Similarly, when the size of the simulation
box is changed, all particles are re-scaled to new positions, unless the
keyword {dilate} is specified with a value of {partial}, in which case
only the particles in the fix group are re-scaled. The latter can be
useful for leaving the coordinates of particles in a solid substrate
unchanged and controlling the pressure of a surrounding fluid.
:line
This fix computes a temperature and pressure each timestep. To do
this, the fix creates its own computes of style "temp/body" and
"pressure", as if these commands had been issued:
compute fix-ID_temp all temp/body
compute fix-ID_press all pressure fix-ID_temp :pre
See the "compute temp/body"_compute_temp_body.html and "compute
pressure"_compute_pressure.html commands for details. Note that the
IDs of the new computes are the fix-ID + underscore + "temp" or fix_ID
+ underscore + "press", and the group for the new computes is "all"
since pressure is computed for the entire system.
Note that these are NOT the computes used by thermodynamic output (see
the "thermo_style"_thermo_style.html command) with ID = {thermo_temp}
and {thermo_press}. This means you can change the attributes of this
fix's temperature or pressure via the
"compute_modify"_compute_modify.html command or print this temperature
or pressure during thermodynamic output via the "thermo_style
custom"_thermo_style.html command using the appropriate compute-ID.
It also means that changing attributes of {thermo_temp} or
{thermo_press} will have no effect on this fix.
:line
Styles with a {cuda}, {gpu}, {intel}, {kk}, {omp}, or {opt} 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 "Section_accelerate"_Section_accelerate.html
of the manual. The accelerated styles take the same arguments and
should produce the same results, except for round-off and precision
issues.
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 "Making
LAMMPS"_Section_start.html#start_3 section for more info.
You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the "-suffix command-line
switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
use the "suffix"_suffix.html command in your input script.
See "Section_accelerate"_Section_accelerate.html of the manual for
more instructions on how to use the accelerated styles effectively.
[Restart, fix_modify, output, run start/stop, minimize info:]
This fix writes the state of the Nose/Hoover barostat to "binary
restart files"_restart.html. See the "read_restart"_read_restart.html
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.
The "fix_modify"_fix_modify.html {temp} and {press} options are
supported by this fix. You can use them to assign a
"compute"_compute.html you have defined to this fix which will be used
in its thermostatting or barostatting procedure. If you do this, note
that the kinetic energy derived from the compute temperature should be
consistent with the virial term computed using all atoms for the
pressure. LAMMPS will warn you if you choose to compute temperature
on a subset of atoms.
The "fix_modify"_fix_modify.html {energy} option is supported by this
fix to add the energy change induced by Nose/Hoover barostatting to
the system's potential energy as part of "thermodynamic
output"_thermo_style.html.
This fix computes the same global scalar and global vector of
quantities as does the "fix nph"_fix_nh.html command.
This fix can ramp its target pressure over multiple runs, using the
{start} and {stop} keywords of the "run"_run.html command. See the
"run"_run.html command for details of how to do this.
This fix is not invoked during "energy minimization"_minimize.html.
[Restrictions:]
This fix is part of the BODY package. It is only enabled if LAMMPS
was built with that package. See the "Making
LAMMPS"_Section_start.html#start_3 section for more info.
This fix requires that atoms store torque and angular momementum and a
quaternion as defined by the "atom_style body"_atom_style.html
command.
[Related commands:]
"fix nph"_fix_nh.html, "fix nve_body"_fix_nve_body.html, "fix
nvt_body"_fix_nvt_body.html, "fix
npt_body"_fix_npt_body.html, "fix_modify"_fix_modify.html
[Default:] none

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@ -0,0 +1,332 @@
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<li class="toctree-l1"><a class="reference internal" href="Section_commands.html">3. Commands</a></li>
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<div class="section" id="fix-npt-body-command">
<span id="index-0"></span><h1>fix npt/body command<a class="headerlink" href="#fix-npt-body-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 npt/body 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>npt/body = style name of this fix command</li>
<li>additional thermostat and barostat related keyword/value pairs from the <a class="reference internal" href="fix_nh.html"><em>fix npt</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 npt/body temp 300.0 300.0 100.0 iso 0.0 0.0 1000.0
fix 2 all npt/body temp 300.0 300.0 100.0 x 5.0 5.0 1000.0
fix 2 all npt/body temp 300.0 300.0 100.0 x 5.0 5.0 1000.0 drag 0.2
fix 2 water npt/body temp 300.0 300.0 100.0 aniso 0.0 0.0 1000.0 dilate partial
</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 NPT integration to update position, velocity,
orientation, and angular velocity each timestep for body
particles in the group using a Nose/Hoover temperature
thermostat and Nose/Hoover pressure barostat. P is pressure; T is
temperature. This creates a system trajectory consistent with the
isothermal-isobaric ensemble.</p>
<p>This fix differs from the <a class="reference internal" href="fix_nh.html"><em>fix npt</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 body 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 and barostat are
specified by keywords and values documented with the <a class="reference internal" href="fix_nh.html"><em>fix npt</em></a> command. See, for example, discussion of the <em>temp</em>,
<em>iso</em>, <em>aniso</em>, and <em>dilate</em> keywords.</p>
<p>The particles in the fix group are the only ones whose velocities and
positions are updated by the velocity/position update portion of the
NPT integration.</p>
<p>Regardless of what particles are in the fix group, a global pressure is
computed for all particles. Similarly, when the size of the simulation
box is changed, all particles are re-scaled to new positions, unless the
keyword <em>dilate</em> is specified with a value of <em>partial</em>, in which case
only the particles in the fix group are re-scaled. The latter can be
useful for leaving the coordinates of particles in a solid substrate
unchanged and controlling the pressure of a surrounding fluid.</p>
<hr class="docutils" />
<p>This fix computes a temperature and pressure each timestep. To do
this, the fix creates its own computes of style &#8220;temp/body&#8221; and
&#8220;pressure&#8221;, as if these commands had been issued:</p>
<div class="highlight-python"><div class="highlight"><pre>compute fix-ID_temp all temp/body
compute fix-ID_press all pressure fix-ID_temp
</pre></div>
</div>
<p>See the <a class="reference internal" href="compute_temp_body.html"><em>compute temp/body</em></a> and <a class="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 + &#8220;temp&#8221; or fix_ID
+ underscore + &#8220;press&#8221;, and the group for the new computes is &#8220;all&#8221;
since pressure is computed for the entire system.</p>
<p>Note that these are NOT the computes 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>
and <em>thermo_press</em>. This means you can change the attributes of this
fix&#8217;s temperature or pressure via the
<a class="reference internal" href="compute_modify.html"><em>compute_modify</em></a> command or print this temperature
or pressure 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> or
<em>thermo_press</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 and barostat
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> and <em>press</em> options are
supported by this fix. You can use them 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 or barostatting procedure. If you do this, note
that the kinetic energy derived from the compute temperature should be
consistent with the virial term computed using all atoms for the
pressure. LAMMPS will warn you if you choose to compute temperature
on a subset of atoms.</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 and
barostatting 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 npt</em></a> command.</p>
<p>This fix can ramp its target temperature and pressure 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 is part of the BODY 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>Making LAMMPS</span></a> section for more info.</p>
<p>This fix requires that atoms store torque and angular momementum and a
quaternion as defined by the <a class="reference internal" href="atom_style.html"><em>atom_style body</em></a>
command.</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 npt</em></a>, <a class="reference internal" href="fix_nve_body.html"><em>fix nve_body</em></a>, <a class="reference internal" href="fix_nvt_body.html"><em>fix nvt_body</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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172
doc/fix_npt_body.txt Executable file
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@ -0,0 +1,172 @@
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)
:line
fix npt/body command :h3
[Syntax:]
fix ID group-ID npt/body keyword value ... :pre
ID, group-ID are documented in "fix"_fix.html command
npt/body = style name of this fix command
additional thermostat and barostat related keyword/value pairs from the "fix npt"_fix_nh.html command can be appended :ul
[Examples:]
fix 1 all npt/body temp 300.0 300.0 100.0 iso 0.0 0.0 1000.0
fix 2 all npt/body temp 300.0 300.0 100.0 x 5.0 5.0 1000.0
fix 2 all npt/body temp 300.0 300.0 100.0 x 5.0 5.0 1000.0 drag 0.2
fix 2 water npt/body temp 300.0 300.0 100.0 aniso 0.0 0.0 1000.0 dilate partial :pre
[Description:]
Perform constant NPT integration to update position, velocity,
orientation, and angular velocity each timestep for body
particles in the group using a Nose/Hoover temperature
thermostat and Nose/Hoover pressure barostat. P is pressure; T is
temperature. This creates a system trajectory consistent with the
isothermal-isobaric ensemble.
This fix differs from the "fix npt"_fix_nh.html command, which
assumes point particles and only updates their position and velocity.
The thermostat is applied to both the translational and rotational
degrees of freedom for the body 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.
Additional parameters affecting the thermostat and barostat are
specified by keywords and values documented with the "fix
npt"_fix_nh.html command. See, for example, discussion of the {temp},
{iso}, {aniso}, and {dilate} keywords.
The particles in the fix group are the only ones whose velocities and
positions are updated by the velocity/position update portion of the
NPT integration.
Regardless of what particles are in the fix group, a global pressure is
computed for all particles. Similarly, when the size of the simulation
box is changed, all particles are re-scaled to new positions, unless the
keyword {dilate} is specified with a value of {partial}, in which case
only the particles in the fix group are re-scaled. The latter can be
useful for leaving the coordinates of particles in a solid substrate
unchanged and controlling the pressure of a surrounding fluid.
:line
This fix computes a temperature and pressure each timestep. To do
this, the fix creates its own computes of style "temp/body" and
"pressure", as if these commands had been issued:
compute fix-ID_temp all temp/body
compute fix-ID_press all pressure fix-ID_temp :pre
See the "compute temp/body"_compute_temp_body.html and "compute
pressure"_compute_pressure.html commands for details. Note that the
IDs of the new computes are the fix-ID + underscore + "temp" or fix_ID
+ underscore + "press", and the group for the new computes is "all"
since pressure is computed for the entire system.
Note that these are NOT the computes used by thermodynamic output (see
the "thermo_style"_thermo_style.html command) with ID = {thermo_temp}
and {thermo_press}. This means you can change the attributes of this
fix's temperature or pressure via the
"compute_modify"_compute_modify.html command or print this temperature
or pressure during thermodynamic output via the "thermo_style
custom"_thermo_style.html command using the appropriate compute-ID.
It also means that changing attributes of {thermo_temp} or
{thermo_press} will have no effect on this fix.
Like other fixes that perform thermostatting, this fix can be used
with "compute commands"_compute.html that calculate a temperature
after removing a "bias" 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 "fix_modify"_fix_modify.html command is used
to assign a temperature compute to this fix that includes such a bias
term. See the doc pages for individual "compute
commands"_compute.html 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.
:line
Styles with a {cuda}, {gpu}, {intel}, {kk}, {omp}, or {opt} 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 "Section_accelerate"_Section_accelerate.html
of the manual. The accelerated styles take the same arguments and
should produce the same results, except for round-off and precision
issues.
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 "Making
LAMMPS"_Section_start.html#start_3 section for more info.
You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the "-suffix command-line
switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
use the "suffix"_suffix.html command in your input script.
See "Section_accelerate"_Section_accelerate.html of the manual for
more instructions on how to use the accelerated styles effectively.
[Restart, fix_modify, output, run start/stop, minimize info:]
This fix writes the state of the Nose/Hoover thermostat and barostat
to "binary restart files"_restart.html. See the
"read_restart"_read_restart.html 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.
The "fix_modify"_fix_modify.html {temp} and {press} options are
supported by this fix. You can use them to assign a
"compute"_compute.html you have defined to this fix which will be used
in its thermostatting or barostatting procedure. If you do this, note
that the kinetic energy derived from the compute temperature should be
consistent with the virial term computed using all atoms for the
pressure. LAMMPS will warn you if you choose to compute temperature
on a subset of atoms.
The "fix_modify"_fix_modify.html {energy} option is supported by this
fix to add the energy change induced by Nose/Hoover thermostatting and
barostatting to the system's potential energy as part of
"thermodynamic output"_thermo_style.html.
This fix computes the same global scalar and global vector of
quantities as does the "fix npt"_fix_nh.html command.
This fix can ramp its target temperature and pressure over multiple
runs, using the {start} and {stop} keywords of the "run"_run.html
command. See the "run"_run.html command for details of how to do
this.
This fix is not invoked during "energy minimization"_minimize.html.
[Restrictions:]
This fix is part of the BODY package. It is only enabled if LAMMPS
was built with that package. See the "Making
LAMMPS"_Section_start.html#start_3 section for more info.
This fix requires that atoms store torque and angular momementum and a
quaternion as defined by the "atom_style body"_atom_style.html
command.
[Related commands:]
"fix npt"_fix_nh.html, "fix nve_body"_fix_nve_body.html, "fix
nvt_body"_fix_nvt_body.html, "fix_modify"_fix_modify.html
[Default:] none

311
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<div class="section" id="fix-nvt-body-command">
<span id="index-0"></span><h1>fix nvt/body command<a class="headerlink" href="#fix-nvt-body-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/body 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/body = 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/body temp 300.0 300.0 100.0
fix 1 all nvt/body 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,
orientation, and angular velocity each timestep for body
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 body 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/body&#8221;, as if this command
had been issued:</p>
<div class="highlight-python"><div class="highlight"><pre>compute fix-ID_temp group-ID temp/body
</pre></div>
</div>
<p>See the <a class="reference internal" href="compute_temp_body.html"><em>compute temp/body</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 is part of the BODY 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>Making LAMMPS</span></a> section for more info.</p>
<p>This fix requires that atoms store torque and angular momementum and a
quaternion as defined by the <a class="reference internal" href="atom_style.html"><em>atom_style body</em></a>
command.</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_body.html"><em>fix nve_body</em></a>, <a class="reference internal" href="fix_npt_body.html"><em>fix npt_body</em></a>, <a class="reference internal" href="fix_modify.html"><em>fix_modify</em></a></p>
<p><strong>Default:</strong> none</p>
</div>
</div>
</div>
</div>
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148
doc/fix_nvt_body.txt Executable file
View File

@ -0,0 +1,148 @@
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)
:line
fix nvt/body command :h3
[Syntax:]
fix ID group-ID nvt/body keyword value ... :pre
ID, group-ID are documented in "fix"_fix.html command
nvt/body = style name of this fix command
additional thermostat related keyword/value pairs from the "fix nvt"_fix_nh.html command can be appended :ul
[Examples:]
fix 1 all nvt/body temp 300.0 300.0 100.0
fix 1 all nvt/body temp 300.0 300.0 100.0 drag 0.2 :pre
[Description:]
Perform constant NVT integration to update position, velocity,
orientation, and angular velocity each timestep for body
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.
This fix differs from the "fix nvt"_fix_nh.html command, which
assumes point particles and only updates their position and velocity.
The thermostat is applied to both the translational and rotational
degrees of freedom for the body 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.
Additional parameters affecting the thermostat are specified by
keywords and values documented with the "fix nvt"_fix_nh.html
command. See, for example, discussion of the {temp} and {drag}
keywords.
This fix computes a temperature each timestep. To do this, the fix
creates its own compute of style "temp/body", as if this command
had been issued:
compute fix-ID_temp group-ID temp/body :pre
See the "compute temp/body"_compute_temp_body.html command for
details. Note that the ID of the new compute is the fix-ID +
underscore + "temp", and the group for the new compute is the same as
the fix group.
Note that this is NOT the compute used by thermodynamic output (see
the "thermo_style"_thermo_style.html command) with ID = {thermo_temp}.
This means you can change the attributes of this fix's temperature
(e.g. its degrees-of-freedom) via the
"compute_modify"_compute_modify.html command or print this temperature
during thermodynamic output via the "thermo_style
custom"_thermo_style.html command using the appropriate compute-ID.
It also means that changing attributes of {thermo_temp} will have no
effect on this fix.
Like other fixes that perform thermostatting, this fix can be used
with "compute commands"_compute.html that calculate a temperature
after removing a "bias" 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 "fix_modify"_fix_modify.html command is used
to assign a temperature compute to this fix that includes such a bias
term. See the doc pages for individual "compute
commands"_compute.html 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.
:line
Styles with a {cuda}, {gpu}, {intel}, {kk}, {omp}, or {opt} 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 "Section_accelerate"_Section_accelerate.html
of the manual. The accelerated styles take the same arguments and
should produce the same results, except for round-off and precision
issues.
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 "Making
LAMMPS"_Section_start.html#start_3 section for more info.
You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the "-suffix command-line
switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
use the "suffix"_suffix.html command in your input script.
See "Section_accelerate"_Section_accelerate.html of the manual for
more instructions on how to use the accelerated styles effectively.
[Restart, fix_modify, output, run start/stop, minimize info:]
This fix writes the state of the Nose/Hoover thermostat to "binary
restart files"_restart.html. See the "read_restart"_read_restart.html
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.
The "fix_modify"_fix_modify.html {temp} option is supported by this
fix. You can use it to assign a "compute"_compute.html you have
defined to this fix which will be used in its thermostatting
procedure.
The "fix_modify"_fix_modify.html {energy} option is supported by this
fix to add the energy change induced by Nose/Hoover thermostatting to
the system's potential energy as part of "thermodynamic
output"_thermo_style.html.
This fix computes the same global scalar and global vector of
quantities as does the "fix nvt"_fix_nh.html command.
This fix can ramp its target temperature over multiple runs, using the
{start} and {stop} keywords of the "run"_run.html command. See the
"run"_run.html command for details of how to do this.
This fix is not invoked during "energy minimization"_minimize.html.
[Restrictions:]
This fix is part of the BODY package. It is only enabled if LAMMPS
was built with that package. See the "Making
LAMMPS"_Section_start.html#start_3 section for more info.
This fix requires that atoms store torque and angular momementum and a
quaternion as defined by the "atom_style body"_atom_style.html
command.
[Related commands:]
"fix nvt"_fix_nh.html, "fix nve_body"_fix_nve_body.html, "fix
npt_body"_fix_npt_body.html, "fix_modify"_fix_modify.html
[Default:] none