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<div class="lammps_version">Version: <b>19 Nov 2024</b></div>
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<li class="toctree-l2"><a class="reference internal" href="angle_coeff.html">angle_coeff command</a></li>
<li class="toctree-l2"><a class="reference internal" href="angle_style.html">angle_style command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="balance.html">balance command</a></li>
<li class="toctree-l2"><a class="reference internal" href="bond_coeff.html">bond_coeff command</a></li>
<li class="toctree-l2"><a class="reference internal" href="bond_style.html">bond_style command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="clear.html">clear command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="compute.html">compute command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="dielectric.html">dielectric command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="minimize.html">minimize command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="neigh_modify.html">neigh_modify command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="set.html">set command</a></li>
<li class="toctree-l2"><a class="reference internal" href="shell.html">shell command</a></li>
<li class="toctree-l2"><a class="reference internal" href="special_bonds.html">special_bonds command</a></li>
<li class="toctree-l2"><a class="reference internal" href="suffix.html">suffix command</a></li>
<li class="toctree-l2"><a class="reference internal" href="tad.html">tad command</a></li>
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<li class="toctree-l2"><a class="reference internal" href="thermo.html">thermo command</a></li>
<li class="toctree-l2"><a class="reference internal" href="thermo_modify.html">thermo_modify command</a></li>
<li class="toctree-l2"><a class="reference internal" href="thermo_style.html">thermo_style command</a></li>
<li class="toctree-l2"><a class="reference internal" href="third_order.html">third_order command</a></li>
<li class="toctree-l2"><a class="reference internal" href="timer.html">timer command</a></li>
<li class="toctree-l2"><a class="reference internal" href="timestep.html">timestep command</a></li>
<li class="toctree-l2"><a class="reference internal" href="uncompute.html">uncompute command</a></li>
<li class="toctree-l2"><a class="reference internal" href="undump.html">undump command</a></li>
<li class="toctree-l2"><a class="reference internal" href="unfix.html">unfix command</a></li>
<li class="toctree-l2"><a class="reference internal" href="units.html">units command</a></li>
<li class="toctree-l2"><a class="reference internal" href="variable.html">variable command</a></li>
<li class="toctree-l2"><a class="reference internal" href="velocity.html">velocity command</a></li>
<li class="toctree-l2"><a class="reference internal" href="write_coeff.html">write_coeff command</a></li>
<li class="toctree-l2"><a class="reference internal" href="write_data.html">write_data command</a></li>
<li class="toctree-l2"><a class="reference internal" href="write_dump.html">write_dump command</a></li>
<li class="toctree-l2"><a class="reference internal" href="write_restart.html">write_restart command</a></li>
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<li class="toctree-l1"><a class="reference internal" href="fixes.html">Fix Styles</a></li>
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<li class="toctree-l1"><a class="reference internal" href="fix_modify_atc_commands.html">fix_modify AtC commands</a></li>
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<p><span class="math notranslate nohighlight">\(\renewcommand{\AA}{\text{Å}}\)</span></p>
<section id="fix-command">
<span id="index-0"></span><h1>fix command<a class="headerlink" href="#fix-command" title="Link to this heading"></a></h1>
<section id="syntax">
<h2>Syntax<a class="headerlink" href="#syntax" title="Link to this heading"></a></h2>
<div class="highlight-LAMMPS notranslate"><div class="highlight"><pre><span></span><span class="k">fix </span><span class="nv nv-Identifier">ID</span><span class="w"> </span><span class="nv nv-Identifier">group-ID</span><span class="w"> </span><span class="n">style</span><span class="w"> </span><span class="n">args</span>
</pre></div>
</div>
<ul class="simple">
<li><p>ID = user-assigned name for the fix</p></li>
<li><p>group-ID = ID of the group of atoms to apply the fix to</p></li>
<li><p>style = one of a long list of possible style names (see below)</p></li>
<li><p>args = arguments used by a particular style</p></li>
</ul>
</section>
<section id="examples">
<h2>Examples<a class="headerlink" href="#examples" title="Link to this heading"></a></h2>
<div class="highlight-LAMMPS notranslate"><div class="highlight"><pre><span></span><span class="k">fix </span><span class="nv nv-Identifier">1</span><span class="w"> </span><span class="nv nv-Identifier">all</span><span class="w"> </span><span class="n">nve</span>
<span class="k">fix </span><span class="nv nv-Identifier">3</span><span class="w"> </span><span class="nv nv-Identifier">all</span><span class="w"> </span><span class="n">nvt</span><span class="w"> </span><span class="n">temp</span><span class="w"> </span><span class="m">300.0</span><span class="w"> </span><span class="m">300.0</span><span class="w"> </span><span class="m">0.01</span>
<span class="k">fix </span><span class="nv nv-Identifier">mine</span><span class="w"> </span><span class="nv nv-Identifier">top</span><span class="w"> </span><span class="n">setforce</span><span class="w"> </span><span class="m">0.0</span><span class="w"> </span><span class="n">NULL</span><span class="w"> </span><span class="m">0.0</span>
</pre></div>
</div>
</section>
<section id="description">
<h2>Description<a class="headerlink" href="#description" title="Link to this heading"></a></h2>
<p>Set a fix that will be applied to a group of atoms. In LAMMPS, a
“fix” is any operation that is applied to the system during
timestepping or minimization. Examples include updating of atom
positions and velocities due to time integration, controlling
temperature, applying constraint forces to atoms, enforcing boundary
conditions, computing diagnostics, etc. There are hundreds of fixes
defined in LAMMPS and new ones can be added; see the
<a class="reference internal" href="Modify.html"><span class="doc">Modify</span></a> page for details.</p>
<p>Fixes perform their operations at different stages of the timestep.
If two or more fixes operate at the same stage of the timestep, they are
invoked in the order they were specified in the input script.</p>
<p>The ID of a fix can only contain alphanumeric characters and
underscores.</p>
<p>Fixes can be deleted with the <a class="reference internal" href="unfix.html"><span class="doc">unfix</span></a> command.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The <a class="reference internal" href="unfix.html"><span class="doc">unfix</span></a> command is the only way to turn off a
fix; simply specifying a new fix with a similar style will not turn
off the first one. This is especially important to realize for
integration fixes. For example, using a <a class="reference internal" href="fix_nve.html"><span class="doc">fix nve</span></a>
command for a second run after using a <a class="reference internal" href="fix_nh.html"><span class="doc">fix nvt</span></a> command
for the first run will not cancel out the NVT time integration
invoked by the “fix nvt” command. Thus, two time integrators would be
in place!</p>
</div>
<p>If you specify a new fix with the same ID and style as an existing
fix, the old fix is deleted and the new one is created (presumably
with new settings). This is the same as if an “unfix” command were
first performed on the old fix, except that the new fix is kept in the
same order relative to the existing fixes as the old one originally
was. Note that this operation also wipes out any additional changes
made to the old fix via the <a class="reference internal" href="fix_modify.html"><span class="doc">fix_modify</span></a> command.</p>
<p>The <a class="reference internal" href="fix_modify.html"><span class="doc">fix modify</span></a> command allows settings for some
fixes to be reset. See the page for individual fixes for details.</p>
<p>Some fixes store an internal “state” which is written to binary
restart files via the <a class="reference internal" href="restart.html"><span class="doc">restart</span></a> or
<a class="reference internal" href="write_restart.html"><span class="doc">write_restart</span></a> commands. This allows the fix to
continue on with its calculations in a restarted simulation. See the
<a class="reference internal" href="read_restart.html"><span class="doc">read_restart</span></a> command for info on how to re-specify
a fix in an input script that reads a restart file. See the doc pages
for individual fixes for info on which ones can be restarted.</p>
<hr class="docutils" />
<p>Some fixes calculate and store any of four <em>styles</em> of quantities:
global, per-atom, local, or per-grid.</p>
<p>A global quantity is one or more system-wide values, e.g. the energy
of a wall interacting with particles. A per-atom quantity is one or
more values per atom, e.g. the original coordinates of each atom at
time 0. Per-atom values are set to 0.0 for atoms not in the specified
fix group. Local quantities are calculated by each processor based on
the atoms it owns, but there may be zero or more per atom, e.g. values
for each bond. Per-grid quantities are calculated on a regular 2d or
3d grid which overlays a 2d or 3d simulation domain. The grid points
and the data they store are distributed across processors; each
processor owns the grid points which fall within its subdomain.</p>
<p>As a general rule of thumb, fixes that produce per-atom quantities
have the word “atom” at the end of their style, e.g. <em>ave/atom</em>.
Fixes that produce local quantities have the word “local” at the end
of their style, e.g. <em>store/local</em>. Fixes that produce per-grid
quantities have the word “grid” at the end of their style,
e.g. <em>ave/grid</em>.</p>
<p>Global, per-atom, local, and per-grid quantities can also be of three
<em>kinds</em>: a single scalar value (global only), a vector of values, or a
2d array of values. For per-atom, local, and per-grid quantities, a
“vector” means a single value for each atom, each local entity
(e.g. bond), or grid cell. Likewise an “array”, means multiple values
for each atom, each local entity, or each grid cell.</p>
<p>Note that a single fix can produce any combination of global,
per-atom, local, or per-grid values. Likewise it can produce any
combination of scalar, vector, or array output for each style. The
exception is that for per-atom, local, and per-grid output, either a
vector or array can be produced, but not both. The doc page for each
fix explains the values it produces, if any.</p>
<p>When a fix output is accessed by another input script command it is
referenced via the following bracket notation, where ID is the ID of
the fix:</p>
<table class="docutils align-default">
<tbody>
<tr class="row-odd"><td><p>f_ID</p></td>
<td><p>entire scalar, vector, or array</p></td>
</tr>
<tr class="row-even"><td><p>f_ID[I]</p></td>
<td><p>one element of vector, one column of array</p></td>
</tr>
<tr class="row-odd"><td><p>f_ID[I][J]</p></td>
<td><p>one element of array</p></td>
</tr>
</tbody>
</table>
<p>In other words, using one bracket reduces the dimension of the
quantity once (vector <span class="math notranslate nohighlight">\(\to\)</span> scalar, array <span class="math notranslate nohighlight">\(\to\)</span> vector).
Using two brackets reduces the dimension twice (array <span class="math notranslate nohighlight">\(\to\)</span>
scalar). Thus, for example, a command that uses global scalar fix
values as input can also process elements of a vector or array.
Depending on the command, this can either be done directly using the
syntax in the table, or by first defining a <a class="reference internal" href="variable.html"><span class="doc">variable</span></a>
of the appropriate style to store the quantity, then using the
variable as an input to the command.</p>
<p>Note that commands and <a class="reference internal" href="variable.html"><span class="doc">variables</span></a> which take fix
outputs as input typically do not allow for all styles and kinds of
data (e.g., a command may require global but not per-atom values, or
it may require a vector of values, not a scalar). This means there is
typically no ambiguity about referring to a fix output as c_ID even if
it produces, for example, both a scalar and vector. The doc pages for
various commands explain the details, including how any ambiguities
are resolved.</p>
<hr class="docutils" />
<p>In LAMMPS, the values generated by a fix can be used in several ways:</p>
<ul class="simple">
<li><p>Global values can be output via the <a class="reference internal" href="thermo_style.html"><span class="doc">thermo_style custom</span></a> or <a class="reference internal" href="fix_ave_time.html"><span class="doc">fix ave/time</span></a> command.
Alternatively, the values can be referenced in an
<a class="reference internal" href="variable.html"><span class="doc">equal-style variable</span></a> command.</p></li>
<li><p>Per-atom values can be output via the <a class="reference internal" href="dump.html"><span class="doc">dump custom</span></a> command,
or they can be time-averaged via the <a class="reference internal" href="fix_ave_atom.html"><span class="doc">fix ave/atom</span></a>
command or reduced by the <a class="reference internal" href="compute_reduce.html"><span class="doc">compute reduce</span></a>
command. Alternatively, per-atom values can be referenced in an
<a class="reference internal" href="variable.html"><span class="doc">atom-style variable</span></a>.</p></li>
<li><p>Local values can be reduced by the <a class="reference internal" href="compute_reduce.html"><span class="doc">compute reduce</span></a>
command or histogrammed by the <a class="reference internal" href="fix_ave_histo.html"><span class="doc">fix ave/histo</span></a> command.
They can also be output by the <a class="reference internal" href="dump.html"><span class="doc">dump local</span></a> command.</p></li>
</ul>
<p>See the <a class="reference internal" href="Howto_output.html"><span class="doc">Howto output</span></a> page for a summary of
various LAMMPS output options, many of which involve fixes.</p>
<p>The results of fixes that calculate global quantities can be either
“intensive” or “extensive” values. Intensive means the value is
independent of the number of atoms in the simulation
(e.g., temperature). Extensive means the value scales with the number of
atoms in the simulation (e.g., total rotational kinetic energy).
<a class="reference internal" href="thermo_style.html"><span class="doc">Thermodynamic output</span></a> will normalize extensive
values by the number of atoms in the system, depending on the
“thermo_modify norm” setting. It will not normalize intensive values.
If a fix value is accessed in another way (e.g., by a
<a class="reference internal" href="variable.html"><span class="doc">variable</span></a>), you may want to know whether it is an
intensive or extensive value. See the page for individual fix styles
for further info.</p>
<hr class="docutils" />
<p>Each fix style has its own page that describes its arguments and
what it does, as listed below. Here is an alphabetical list of fix
styles available in LAMMPS. They are also listed in more compact form
on the <a class="reference internal" href="Commands_fix.html"><span class="doc">Commands fix</span></a> doc page.</p>
<p>There are also additional accelerated fix styles included in the
LAMMPS distribution for faster performance on CPUs, GPUs, and KNLs.
The individual style names on the <a class="reference internal" href="Commands_fix.html"><span class="doc">Commands fix</span></a> doc
page are followed by one or more of (g,i,k,o,t) to indicate which
accelerated styles exist.</p>
<ul class="simple">
<li><p><a class="reference internal" href="fix_accelerate_cos.html"><span class="doc">accelerate/cos</span></a> - apply cosine-shaped acceleration to atoms</p></li>
<li><p><a class="reference internal" href="fix_acks2_reaxff.html"><span class="doc">acks2/reaxff</span></a> - apply ACKS2 charge equilibration</p></li>
<li><p><a class="reference internal" href="fix_adapt.html"><span class="doc">adapt</span></a> - change a simulation parameter over time</p></li>
<li><p><a class="reference internal" href="fix_adapt_fep.html"><span class="doc">adapt/fep</span></a> - enhanced version of fix adapt</p></li>
<li><p><a class="reference internal" href="fix_addforce.html"><span class="doc">addforce</span></a> - add a force to each atom</p></li>
<li><p><a class="reference internal" href="fix_add_heat.html"><span class="doc">add/heat</span></a> - add a heat flux to each atom</p></li>
<li><p><a class="reference internal" href="fix_addtorque.html"><span class="doc">addtorque</span></a> - add a torque to a group of atoms</p></li>
<li><p><a class="reference internal" href="fix_alchemy.html"><span class="doc">alchemy</span></a> - perform an “alchemical transformation” between two partitions</p></li>
<li><p><a class="reference internal" href="fix_amoeba_bitorsion.html"><span class="doc">amoeba/bitorsion</span></a> - torsion/torsion terms in AMOEBA force field</p></li>
<li><p><a class="reference internal" href="fix_amoeba_pitorsion.html"><span class="doc">amoeba/pitorsion</span></a> - 6-body terms in AMOEBA force field</p></li>
<li><p><a class="reference internal" href="fix_append_atoms.html"><span class="doc">append/atoms</span></a> - append atoms to a running simulation</p></li>
<li><p><a class="reference internal" href="fix_atc.html"><span class="doc">atc</span></a> - initiates a coupled MD/FE simulation</p></li>
<li><p><a class="reference internal" href="fix_atom_swap.html"><span class="doc">atom/swap</span></a> - Monte Carlo atom type swapping</p></li>
<li><p><a class="reference internal" href="fix_ave_atom.html"><span class="doc">ave/atom</span></a> - compute per-atom time-averaged quantities</p></li>
<li><p><a class="reference internal" href="fix_ave_chunk.html"><span class="doc">ave/chunk</span></a> - compute per-chunk time-averaged quantities</p></li>
<li><p><a class="reference internal" href="fix_ave_correlate.html"><span class="doc">ave/correlate</span></a> - compute/output time correlations</p></li>
<li><p><a class="reference internal" href="fix_ave_correlate_long.html"><span class="doc">ave/correlate/long</span></a> - alternative to <a class="reference internal" href="fix_ave_correlate.html"><span class="doc">ave/correlate</span></a> that allows efficient calculation over long time windows</p></li>
<li><p><a class="reference internal" href="fix_ave_grid.html"><span class="doc">ave/grid</span></a> - compute per-grid time-averaged quantities</p></li>
<li><p><a class="reference internal" href="fix_ave_histo.html"><span class="doc">ave/histo</span></a> - compute/output time-averaged histograms</p></li>
<li><p><a class="reference internal" href="fix_ave_histo.html"><span class="doc">ave/histo/weight</span></a> - weighted version of fix ave/histo</p></li>
<li><p><a class="reference internal" href="fix_ave_time.html"><span class="doc">ave/time</span></a> - compute/output global time-averaged quantities</p></li>
<li><p><a class="reference internal" href="fix_aveforce.html"><span class="doc">aveforce</span></a> - add an averaged force to each atom</p></li>
<li><p><a class="reference internal" href="fix_balance.html"><span class="doc">balance</span></a> - perform dynamic load-balancing</p></li>
<li><p><a class="reference internal" href="fix_brownian.html"><span class="doc">brownian</span></a> - overdamped translational brownian motion</p></li>
<li><p><a class="reference internal" href="fix_brownian.html"><span class="doc">brownian/asphere</span></a> - overdamped translational and rotational brownian motion for ellipsoids</p></li>
<li><p><a class="reference internal" href="fix_brownian.html"><span class="doc">brownian/sphere</span></a> - overdamped translational and rotational brownian motion for spheres</p></li>
<li><p><a class="reference internal" href="fix_bocs.html"><span class="doc">bocs</span></a> - NPT style time integration with pressure correction</p></li>
<li><p><a class="reference internal" href="fix_bond_break.html"><span class="doc">bond/break</span></a> - break bonds on the fly</p></li>
<li><p><a class="reference internal" href="fix_bond_create.html"><span class="doc">bond/create</span></a> - create bonds on the fly</p></li>
<li><p><a class="reference internal" href="fix_bond_create.html"><span class="doc">bond/create/angle</span></a> - create bonds on the fly with angle constraints</p></li>
<li><p><a class="reference internal" href="fix_bond_react.html"><span class="doc">bond/react</span></a> - apply topology changes to model reactions</p></li>
<li><p><a class="reference internal" href="fix_bond_swap.html"><span class="doc">bond/swap</span></a> - Monte Carlo bond swapping</p></li>
<li><p><a class="reference internal" href="fix_box_relax.html"><span class="doc">box/relax</span></a> - relax box size during energy minimization</p></li>
<li><p><a class="reference internal" href="fix_charge_regulation.html"><span class="doc">charge/regulation</span></a> - Monte Carlo sampling of charge regulation</p></li>
<li><p><a class="reference internal" href="fix_cmap.html"><span class="doc">cmap</span></a> - CMAP torsion/torsion terms in CHARMM force field</p></li>
<li><p><a class="reference internal" href="fix_colvars.html"><span class="doc">colvars</span></a> - interface to the collective variables “Colvars” library</p></li>
<li><p><a class="reference internal" href="fix_controller.html"><span class="doc">controller</span></a> - apply control loop feedback mechanism</p></li>
<li><p><a class="reference internal" href="fix_damping_cundall.html"><span class="doc">damping/cundall</span></a> - Cundall non-viscous damping for granular simulations</p></li>
<li><p><a class="reference internal" href="fix_deform.html"><span class="doc">deform</span></a> - change the simulation box size/shape</p></li>
<li><p><a class="reference internal" href="fix_deform_pressure.html"><span class="doc">deform/pressure</span></a> - change the simulation box size/shape with additional loading conditions</p></li>
<li><p><a class="reference internal" href="fix_deposit.html"><span class="doc">deposit</span></a> - add new atoms above a surface</p></li>
<li><p><a class="reference internal" href="fix_dpd_energy.html"><span class="doc">dpd/energy</span></a> - constant energy dissipative particle dynamics</p></li>
<li><p><a class="reference internal" href="fix_drag.html"><span class="doc">drag</span></a> - drag atoms towards a defined coordinate</p></li>
<li><p><a class="reference internal" href="fix_drude.html"><span class="doc">drude</span></a> - part of Drude oscillator polarization model</p></li>
<li><p><a class="reference internal" href="fix_drude_transform.html"><span class="doc">drude/transform/direct</span></a> - part of Drude oscillator polarization model</p></li>
<li><p><a class="reference internal" href="fix_drude_transform.html"><span class="doc">drude/transform/inverse</span></a> - part of Drude oscillator polarization model</p></li>
<li><p><a class="reference internal" href="fix_dt_reset.html"><span class="doc">dt/reset</span></a> - reset the timestep based on velocity, forces</p></li>
<li><p><a class="reference internal" href="fix_dpd_source.html"><span class="doc">edpd/source</span></a> - add heat source to eDPD simulations</p></li>
<li><p><a class="reference internal" href="fix_efield.html"><span class="doc">efield</span></a> - impose electric field on system</p></li>
<li><p><a class="reference internal" href="fix_efield.html"><span class="doc">efield/tip4p</span></a> - impose electric field on system with TIP4P molecules</p></li>
<li><p><a class="reference internal" href="fix_ehex.html"><span class="doc">ehex</span></a> - enhanced heat exchange algorithm</p></li>
<li><p><a class="reference internal" href="fix_electrode.html"><span class="doc">electrode/conp</span></a> - impose electric potential</p></li>
<li><p><a class="reference internal" href="fix_electrode.html"><span class="doc">electrode/conq</span></a> - impose total electric charge</p></li>
<li><p><a class="reference internal" href="fix_electrode.html"><span class="doc">electrode/thermo</span></a> - apply thermo-potentiostat</p></li>
<li><p><a class="reference internal" href="fix_electron_stopping.html"><span class="doc">electron/stopping</span></a> - electronic stopping power as a friction force</p></li>
<li><p><a class="reference internal" href="fix_electron_stopping.html"><span class="doc">electron/stopping/fit</span></a> - electronic stopping power as a friction force</p></li>
<li><p><a class="reference internal" href="fix_enforce2d.html"><span class="doc">enforce2d</span></a> - zero out <em>z</em>-dimension velocity and force</p></li>
<li><p><a class="reference internal" href="fix_eos_cv.html"><span class="doc">eos/cv</span></a> - applies a mesoparticle equation of state to relate the particle internal energy to the particle internal temperature</p></li>
<li><p><a class="reference internal" href="fix_eos_table.html"><span class="doc">eos/table</span></a> - applies a tabulated mesoparticle equation of state to relate the particle internal energy to the particle internal temperature</p></li>
<li><p><a class="reference internal" href="fix_eos_table_rx.html"><span class="doc">eos/table/rx</span></a> - applies a tabulated mesoparticle equation of state to relate the concentration-dependent particle internal energy to the particle internal temperature</p></li>
<li><p><a class="reference internal" href="fix_evaporate.html"><span class="doc">evaporate</span></a> - remove atoms from simulation periodically</p></li>
<li><p><a class="reference internal" href="fix_external.html"><span class="doc">external</span></a> - callback to an external driver program</p></li>
<li><p><a class="reference internal" href="fix_ffl.html"><span class="doc">ffl</span></a> - apply a Fast-Forward Langevin equation thermostat</p></li>
<li><p><a class="reference internal" href="fix_filter_corotate.html"><span class="doc">filter/corotate</span></a> - implement corotation filter to allow larger timesteps with r-RESPA</p></li>
<li><p><a class="reference internal" href="fix_flow_gauss.html"><span class="doc">flow/gauss</span></a> - Gaussian dynamics for constant mass flux</p></li>
<li><p><a class="reference internal" href="fix_freeze.html"><span class="doc">freeze</span></a> - freeze atoms in a granular simulation</p></li>
<li><p><a class="reference internal" href="fix_gcmc.html"><span class="doc">gcmc</span></a> - grand canonical insertions/deletions</p></li>
<li><p><a class="reference internal" href="fix_gld.html"><span class="doc">gld</span></a> - generalized Langevin dynamics integrator</p></li>
<li><p><a class="reference internal" href="fix_gle.html"><span class="doc">gle</span></a> - generalized Langevin equation thermostat</p></li>
<li><p><a class="reference internal" href="fix_gravity.html"><span class="doc">gravity</span></a> - add gravity to atoms in a granular simulation</p></li>
<li><p><a class="reference internal" href="fix_grem.html"><span class="doc">grem</span></a> - implements the generalized replica exchange method</p></li>
<li><p><a class="reference internal" href="fix_halt.html"><span class="doc">halt</span></a> - terminate a dynamics run or minimization</p></li>
<li><p><a class="reference internal" href="fix_heat.html"><span class="doc">heat</span></a> - add/subtract momentum-conserving heat</p></li>
<li><p><a class="reference internal" href="fix_heat_flow.html"><span class="doc">heat/flow</span></a> - plain time integration of heat flow with per-atom temperature updates</p></li>
<li><p><a class="reference internal" href="fix_hyper_global.html"><span class="doc">hyper/global</span></a> - global hyperdynamics</p></li>
<li><p><a class="reference internal" href="fix_hyper_local.html"><span class="doc">hyper/local</span></a> - local hyperdynamics</p></li>
<li><p><a class="reference internal" href="fix_imd.html"><span class="doc">imd</span></a> - implements the “Interactive MD” (IMD) protocol</p></li>
<li><p><a class="reference internal" href="fix_indent.html"><span class="doc">indent</span></a> - impose force due to an indenter</p></li>
<li><p><a class="reference internal" href="fix_ipi.html"><span class="doc">ipi</span></a> - enable LAMMPS to run as a client for i-PI path-integral simulations</p></li>
<li><p><a class="reference internal" href="fix_langevin.html"><span class="doc">langevin</span></a> - Langevin temperature control</p></li>
<li><p><a class="reference internal" href="fix_langevin_drude.html"><span class="doc">langevin/drude</span></a> - Langevin temperature control of Drude oscillators</p></li>
<li><p><a class="reference internal" href="fix_langevin_eff.html"><span class="doc">langevin/eff</span></a> - Langevin temperature control for the electron force field model</p></li>
<li><p><a class="reference internal" href="fix_langevin_spin.html"><span class="doc">langevin/spin</span></a> - Langevin temperature control for a spin or spin-lattice system</p></li>
<li><p><a class="reference internal" href="fix_lb_fluid.html"><span class="doc">lb/fluid</span></a> - lattice-Boltzmann fluid on a uniform mesh</p></li>
<li><p><a class="reference internal" href="fix_lb_momentum.html"><span class="doc">lb/momentum</span></a> - <a class="reference internal" href="fix_momentum.html"><span class="doc">fix momentum</span></a> replacement for use with a lattice-Boltzmann fluid</p></li>
<li><p><a class="reference internal" href="fix_lb_viscous.html"><span class="doc">lb/viscous</span></a> - <a class="reference internal" href="fix_viscous.html"><span class="doc">fix viscous</span></a> replacement for use with a lattice-Boltzmann fluid</p></li>
<li><p><a class="reference internal" href="fix_lineforce.html"><span class="doc">lineforce</span></a> - constrain atoms to move in a line</p></li>
<li><p><a class="reference internal" href="fix_manifoldforce.html"><span class="doc">manifoldforce</span></a> - restrain atoms to a manifold during minimization</p></li>
<li><p><a class="reference internal" href="fix_mdi_qm.html"><span class="doc">mdi/qm</span></a> - LAMMPS operates as a client for a quantum code via the MolSSI Driver Interface (MDI)</p></li>
<li><p><a class="reference internal" href="fix_mdi_qmmm.html"><span class="doc">mdi/qmmm</span></a> - LAMMPS operates as client for QM/MM simulation with a quantum code via the MolSSI Driver Interface (MDI)</p></li>
<li><p><a class="reference internal" href="fix_meso_move.html"><span class="doc">meso/move</span></a> - move mesoscopic SPH/SDPD particles in a prescribed fashion</p></li>
<li><p><a class="reference internal" href="fix_mol_swap.html"><span class="doc">mol/swap</span></a> - Monte Carlo atom type swapping with a molecule</p></li>
<li><p><a class="reference internal" href="fix_momentum.html"><span class="doc">momentum</span></a> - zero the linear and/or angular momentum of a group of atoms</p></li>
<li><p><a class="reference internal" href="fix_momentum.html"><span class="doc">momentum/chunk</span></a> - zero the linear and/or angular momentum of a chunk of atoms</p></li>
<li><p><a class="reference internal" href="fix_move.html"><span class="doc">move</span></a> - move atoms in a prescribed fashion</p></li>
<li><p><a class="reference internal" href="fix_msst.html"><span class="doc">msst</span></a> - multi-scale shock technique (MSST) integration</p></li>
<li><p><a class="reference internal" href="fix_mvv_dpd.html"><span class="doc">mvv/dpd</span></a> - DPD using the modified velocity-Verlet integration algorithm</p></li>
<li><p><a class="reference internal" href="fix_mvv_dpd.html"><span class="doc">mvv/edpd</span></a> - constant energy DPD using the modified velocity-Verlet algorithm</p></li>
<li><p><a class="reference internal" href="fix_mvv_dpd.html"><span class="doc">mvv/tdpd</span></a> - constant temperature DPD using the modified velocity-Verlet algorithm</p></li>
<li><p><a class="reference internal" href="fix_neb.html"><span class="doc">neb</span></a> - nudged elastic band (NEB) spring forces</p></li>
<li><p><a class="reference internal" href="fix_neb_spin.html"><span class="doc">neb/spin</span></a> - nudged elastic band (NEB) spring forces for spins</p></li>
<li><p><a class="reference internal" href="fix_nonaffine_displacement.html"><span class="doc">nonaffine/displacement</span></a> - calculate nonaffine displacement of atoms</p></li>
<li><p><a class="reference internal" href="fix_nh.html"><span class="doc">nph</span></a> - constant NPH time integration via Nose/Hoover</p></li>
<li><p><a class="reference internal" href="fix_nph_asphere.html"><span class="doc">nph/asphere</span></a> - NPH for aspherical particles</p></li>
<li><p><a class="reference internal" href="fix_nph_body.html"><span class="doc">nph/body</span></a> - NPH for body particles</p></li>
<li><p><a class="reference internal" href="fix_nh_eff.html"><span class="doc">nph/eff</span></a> - NPH for nuclei and electrons in the electron force field model</p></li>
<li><p><a class="reference internal" href="fix_nph_sphere.html"><span class="doc">nph/sphere</span></a> - NPH for spherical particles</p></li>
<li><p><a class="reference internal" href="fix_nphug.html"><span class="doc">nphug</span></a> - constant-stress Hugoniostat integration</p></li>
<li><p><a class="reference internal" href="fix_nh.html"><span class="doc">npt</span></a> - constant NPT time integration via Nose/Hoover</p></li>
<li><p><a class="reference internal" href="fix_npt_asphere.html"><span class="doc">npt/asphere</span></a> - NPT for aspherical particles</p></li>
<li><p><a class="reference internal" href="fix_npt_body.html"><span class="doc">npt/body</span></a> - NPT for body particles</p></li>
<li><p><a class="reference internal" href="fix_npt_cauchy.html"><span class="doc">npt/cauchy</span></a> - NPT with Cauchy stress</p></li>
<li><p><a class="reference internal" href="fix_nh_eff.html"><span class="doc">npt/eff</span></a> - NPT for nuclei and electrons in the electron force field model</p></li>
<li><p><a class="reference internal" href="fix_npt_sphere.html"><span class="doc">npt/sphere</span></a> - NPT for spherical particles</p></li>
<li><p><a class="reference internal" href="fix_nh_uef.html"><span class="doc">npt/uef</span></a> - NPT style time integration with diagonal flow</p></li>
<li><p><a class="reference internal" href="fix_numdiff.html"><span class="doc">numdiff</span></a> - numerically approximate atomic forces using finite energy differences</p></li>
<li><p><a class="reference internal" href="fix_numdiff_virial.html"><span class="doc">numdiff/virial</span></a> - numerically approximate virial stress tensor using finite energy differences</p></li>
<li><p><a class="reference internal" href="fix_nve.html"><span class="doc">nve</span></a> - constant NVE time integration</p></li>
<li><p><a class="reference internal" href="fix_nve_asphere.html"><span class="doc">nve/asphere</span></a> - NVE for aspherical particles</p></li>
<li><p><a class="reference internal" href="fix_nve_asphere_noforce.html"><span class="doc">nve/asphere/noforce</span></a> - NVE for aspherical particles without forces</p></li>
<li><p><a class="reference internal" href="fix_nve_awpmd.html"><span class="doc">nve/awpmd</span></a> - NVE for the Antisymmetrized Wave Packet Molecular Dynamics model</p></li>
<li><p><a class="reference internal" href="fix_nve_body.html"><span class="doc">nve/body</span></a> - NVE for body particles</p></li>
<li><p><a class="reference internal" href="fix_nve_dot.html"><span class="doc">nve/dot</span></a> - rigid body constant energy time integrator for coarse grain models</p></li>
<li><p><a class="reference internal" href="fix_nve_dotc_langevin.html"><span class="doc">nve/dotc/langevin</span></a> - Langevin style rigid body time integrator for coarse grain models</p></li>
<li><p><a class="reference internal" href="fix_nve_eff.html"><span class="doc">nve/eff</span></a> - NVE for nuclei and electrons in the electron force field model</p></li>
<li><p><a class="reference internal" href="fix_nve_limit.html"><span class="doc">nve/limit</span></a> - NVE with limited step length</p></li>
<li><p><a class="reference internal" href="fix_nve_line.html"><span class="doc">nve/line</span></a> - NVE for line segments</p></li>
<li><p><a class="reference internal" href="fix_nve_manifold_rattle.html"><span class="doc">nve/manifold/rattle</span></a> - NVE time integration for atoms constrained to a curved surface (manifold)</p></li>
<li><p><a class="reference internal" href="fix_nve_noforce.html"><span class="doc">nve/noforce</span></a> - NVE without forces (update positions only)</p></li>
<li><p><a class="reference internal" href="fix_nve_sphere.html"><span class="doc">nve/sphere</span></a> - NVE for spherical particles</p></li>
<li><p><a class="reference internal" href="fix_nve_bpm_sphere.html"><span class="doc">nve/bpm/sphere</span></a> - NVE for spherical particles used in the BPM package</p></li>
<li><p><a class="reference internal" href="fix_nve_spin.html"><span class="doc">nve/spin</span></a> - NVE for a spin or spin-lattice system</p></li>
<li><p><a class="reference internal" href="fix_nve_tri.html"><span class="doc">nve/tri</span></a> - NVE for triangles</p></li>
<li><p><a class="reference internal" href="fix_nvk.html"><span class="doc">nvk</span></a> - constant kinetic energy time integration</p></li>
<li><p><a class="reference internal" href="fix_nh.html"><span class="doc">nvt</span></a> - NVT time integration via Nose/Hoover</p></li>
<li><p><a class="reference internal" href="fix_nvt_asphere.html"><span class="doc">nvt/asphere</span></a> - NVT for aspherical particles</p></li>
<li><p><a class="reference internal" href="fix_nvt_body.html"><span class="doc">nvt/body</span></a> - NVT for body particles</p></li>
<li><p><a class="reference internal" href="fix_nh_eff.html"><span class="doc">nvt/eff</span></a> - NVE for nuclei and electrons in the electron force field model</p></li>
<li><p><a class="reference internal" href="fix_nvt_manifold_rattle.html"><span class="doc">nvt/manifold/rattle</span></a> - NVT time integration for atoms constrained to a curved surface (manifold)</p></li>
<li><p><a class="reference internal" href="fix_nvt_sllod.html"><span class="doc">nvt/sllod</span></a> - NVT for NEMD with SLLOD equations</p></li>
<li><p><a class="reference internal" href="fix_nvt_sllod_eff.html"><span class="doc">nvt/sllod/eff</span></a> - NVT for NEMD with SLLOD equations for the electron force field model</p></li>
<li><p><a class="reference internal" href="fix_nvt_sphere.html"><span class="doc">nvt/sphere</span></a> - NVT for spherical particles</p></li>
<li><p><a class="reference internal" href="fix_nh_uef.html"><span class="doc">nvt/uef</span></a> - NVT style time integration with diagonal flow</p></li>
<li><p><a class="reference internal" href="fix_oneway.html"><span class="doc">oneway</span></a> - constrain particles on move in one direction</p></li>
<li><p><a class="reference internal" href="fix_orient.html"><span class="doc">orient/bcc</span></a> - add grain boundary migration force for BCC</p></li>
<li><p><a class="reference internal" href="fix_orient.html"><span class="doc">orient/fcc</span></a> - add grain boundary migration force for FCC</p></li>
<li><p><a class="reference internal" href="fix_orient_eco.html"><span class="doc">orient/eco</span></a> - add generalized grain boundary migration force</p></li>
<li><p><a class="reference internal" href="fix_pafi.html"><span class="doc">pafi</span></a> - constrained force averages on hyper-planes to compute free energies (PAFI)</p></li>
<li><p><a class="reference internal" href="fix_pair.html"><span class="doc">pair</span></a> - access per-atom info from pair styles</p></li>
<li><p><a class="reference internal" href="fix_phonon.html"><span class="doc">phonon</span></a> - calculate dynamical matrix from MD simulations</p></li>
<li><p><a class="reference internal" href="fix_pimd.html"><span class="doc">pimd/langevin</span></a> - Feynman path-integral molecular dynamics with stochastic thermostat</p></li>
<li><p><a class="reference internal" href="fix_pimd.html"><span class="doc">pimd/nvt</span></a> - Feynman path-integral molecular dynamics with Nose-Hoover thermostat</p></li>
<li><p><a class="reference internal" href="fix_pimdb.html"><span class="doc">pimdb/langevin</span></a> - Bosonic Feynman path-integral molecular dynamics for with stochastic thermostat</p></li>
<li><p><a class="reference internal" href="fix_pimdb.html"><span class="doc">pimdb/nvt</span></a> - Bosonic Feynman path-integral molecular dynamics with Nose-Hoover thermostat</p></li>
<li><p><a class="reference internal" href="fix_planeforce.html"><span class="doc">planeforce</span></a> - constrain atoms to move in a plane</p></li>
<li><p><a class="reference internal" href="fix_plumed.html"><span class="doc">plumed</span></a> - wrapper on PLUMED free energy library</p></li>
<li><p><a class="reference internal" href="fix_poems.html"><span class="doc">poems</span></a> - constrain clusters of atoms to move as coupled rigid bodies</p></li>
<li><p><a class="reference internal" href="fix_polarize.html"><span class="doc">polarize/bem/gmres</span></a> - compute induced charges at the interface between impermeable media with different dielectric constants with generalized minimum residual (GMRES)</p></li>
<li><p><a class="reference internal" href="fix_polarize.html"><span class="doc">polarize/bem/icc</span></a> - compute induced charges at the interface between impermeable media with different dielectric constants with the successive over-relaxation algorithm</p></li>
<li><p><a class="reference internal" href="fix_polarize.html"><span class="doc">polarize/functional</span></a> - compute induced charges at the interface between impermeable media with different dielectric constants with the energy variational approach</p></li>
<li><p><a class="reference internal" href="fix_pour.html"><span class="doc">pour</span></a> - pour new atoms/molecules into a granular simulation domain</p></li>
<li><p><a class="reference internal" href="fix_precession_spin.html"><span class="doc">precession/spin</span></a> - apply a precession torque to each magnetic spin</p></li>
<li><p><a class="reference internal" href="fix_press_berendsen.html"><span class="doc">press/berendsen</span></a> - pressure control by Berendsen barostat</p></li>
<li><p><a class="reference internal" href="fix_press_langevin.html"><span class="doc">press/langevin</span></a> - pressure control by Langevin barostat</p></li>
<li><p><a class="reference internal" href="fix_print.html"><span class="doc">print</span></a> - print text and variables during a simulation</p></li>
<li><p><a class="reference internal" href="fix_propel_self.html"><span class="doc">propel/self</span></a> - model self-propelled particles</p></li>
<li><p><a class="reference internal" href="fix_property_atom.html"><span class="doc">property/atom</span></a> - add customized per-atom values</p></li>
<li><p><a class="reference internal" href="fix_python_invoke.html"><span class="doc">python/invoke</span></a> - call a Python function during a simulation</p></li>
<li><p><a class="reference internal" href="fix_python_move.html"><span class="doc">python/move</span></a> - move particles using a Python function during a simulation run</p></li>
<li><p><a class="reference internal" href="fix_qbmsst.html"><span class="doc">qbmsst</span></a> - quantum bath multi-scale shock technique time integrator</p></li>
<li><p><a class="reference internal" href="fix_qeq_comb.html"><span class="doc">qeq/comb</span></a> - charge equilibration for COMB potential</p></li>
<li><p><a class="reference internal" href="fix_qeq.html"><span class="doc">qeq/ctip</span></a> - charge equilibration for CTIP potential</p></li>
<li><p><a class="reference internal" href="fix_qeq.html"><span class="doc">qeq/dynamic</span></a> - charge equilibration via dynamic method</p></li>
<li><p><a class="reference internal" href="fix_qeq.html"><span class="doc">qeq/fire</span></a> - charge equilibration via FIRE minimizer</p></li>
<li><p><a class="reference internal" href="fix_qeq.html"><span class="doc">qeq/point</span></a> - charge equilibration via point method</p></li>
<li><p><a class="reference internal" href="fix_qeq_reaxff.html"><span class="doc">qeq/reaxff</span></a> - charge equilibration for ReaxFF potential</p></li>
<li><p><a class="reference internal" href="fix_qeq.html"><span class="doc">qeq/shielded</span></a> - charge equilibration via shielded method</p></li>
<li><p><a class="reference internal" href="fix_qeq.html"><span class="doc">qeq/slater</span></a> - charge equilibration via Slater method</p></li>
<li><p><a class="reference internal" href="fix_qmmm.html"><span class="doc">qmmm</span></a> - functionality to enable a quantum mechanics/molecular mechanics coupling</p></li>
<li><p><a class="reference internal" href="fix_qtb.html"><span class="doc">qtb</span></a> - implement quantum thermal bath scheme</p></li>
<li><p><a class="reference internal" href="fix_qtpie_reaxff.html"><span class="doc">qtpie/reaxff</span></a> - apply QTPIE charge equilibration</p></li>
<li><p><a class="reference internal" href="fix_shake.html"><span class="doc">rattle</span></a> - RATTLE constraints on bonds and/or angles</p></li>
<li><p><a class="reference internal" href="fix_reaxff_bonds.html"><span class="doc">reaxff/bonds</span></a> - write out ReaxFF bond information</p></li>
<li><p><a class="reference internal" href="fix_reaxff_species.html"><span class="doc">reaxff/species</span></a> - write out ReaxFF molecule information</p></li>
<li><p><a class="reference internal" href="fix_recenter.html"><span class="doc">recenter</span></a> - constrain the center-of-mass position of a group of atoms</p></li>
<li><p><a class="reference internal" href="fix_restrain.html"><span class="doc">restrain</span></a> - constrain a bond, angle, dihedral</p></li>
<li><p><a class="reference internal" href="fix_rheo.html"><span class="doc">rheo</span></a> - integrator for the RHEO package</p></li>
<li><p><a class="reference internal" href="fix_rheo_thermal.html"><span class="doc">rheo/thermal</span></a> - thermal integrator for the RHEO package</p></li>
<li><p><a class="reference internal" href="fix_rheo_oxidation.html"><span class="doc">rheo/oxidation</span></a> - create oxidation bonds for the RHEO package</p></li>
<li><p><a class="reference internal" href="fix_rheo_pressure.html"><span class="doc">rheo/pressure</span></a> - pressure calculation for the RHEO package</p></li>
<li><p><a class="reference internal" href="fix_rheo_pressure.html"><span class="doc">rheo/viscosity</span></a> - viscosity calculation for the RHEO package</p></li>
<li><p><a class="reference internal" href="fix_rhok.html"><span class="doc">rhok</span></a> - add bias potential for long-range ordered systems</p></li>
<li><p><a class="reference internal" href="fix_rigid.html"><span class="doc">rigid</span></a> - constrain one or more clusters of atoms to move as a rigid body with NVE integration</p></li>
<li><p><a class="reference internal" href="fix_rigid_meso.html"><span class="doc">rigid/meso</span></a> - constrain clusters of mesoscopic SPH/SDPD particles to move as a rigid body</p></li>
<li><p><a class="reference internal" href="fix_rigid.html"><span class="doc">rigid/nph</span></a> - constrain one or more clusters of atoms to move as a rigid body with NPH integration</p></li>
<li><p><a class="reference internal" href="fix_rigid.html"><span class="doc">rigid/nph/small</span></a> - constrain many small clusters of atoms to move as a rigid body with NPH integration</p></li>
<li><p><a class="reference internal" href="fix_rigid.html"><span class="doc">rigid/npt</span></a> - constrain one or more clusters of atoms to move as a rigid body with NPT integration</p></li>
<li><p><a class="reference internal" href="fix_rigid.html"><span class="doc">rigid/npt/small</span></a> - constrain many small clusters of atoms to move as a rigid body with NPT integration</p></li>
<li><p><a class="reference internal" href="fix_rigid.html"><span class="doc">rigid/nve</span></a> - constrain one or more clusters of atoms to move as a rigid body with alternate NVE integration</p></li>
<li><p><a class="reference internal" href="fix_rigid.html"><span class="doc">rigid/nve/small</span></a> - constrain many small clusters of atoms to move as a rigid body with alternate NVE integration</p></li>
<li><p><a class="reference internal" href="fix_rigid.html"><span class="doc">rigid/nvt</span></a> - constrain one or more clusters of atoms to move as a rigid body with NVT integration</p></li>
<li><p><a class="reference internal" href="fix_rigid.html"><span class="doc">rigid/nvt/small</span></a> - constrain many small clusters of atoms to move as a rigid body with NVT integration</p></li>
<li><p><a class="reference internal" href="fix_rigid.html"><span class="doc">rigid/small</span></a> - constrain many small clusters of atoms to move as a rigid body with NVE integration</p></li>
<li><p><a class="reference internal" href="fix_rx.html"><span class="doc">rx</span></a> - solve reaction kinetic ODEs for a defined reaction set</p></li>
<li><p><a class="reference internal" href="fix_saed_vtk.html"><span class="doc">saed/vtk</span></a> - time-average the intensities from <a class="reference internal" href="compute_saed.html"><span class="doc">compute saed</span></a></p></li>
<li><p><a class="reference internal" href="fix_setforce.html"><span class="doc">setforce</span></a> - set the force on each atom</p></li>
<li><p><a class="reference internal" href="fix_setforce.html"><span class="doc">setforce/spin</span></a> - set magnetic precession vectors on each atom</p></li>
<li><p><a class="reference internal" href="fix_sgcmc.html"><span class="doc">sgcmc</span></a> - fix for hybrid semi-grand canonical MD/MC simulations</p></li>
<li><p><a class="reference internal" href="fix_shake.html"><span class="doc">shake</span></a> - SHAKE constraints on bonds and/or angles</p></li>
<li><p><a class="reference internal" href="fix_shardlow.html"><span class="doc">shardlow</span></a> - integration of DPD equations of motion using the Shardlow splitting</p></li>
<li><p><a class="reference internal" href="fix_smd.html"><span class="doc">smd</span></a> - applied a steered MD force to a group</p></li>
<li><p><a class="reference internal" href="fix_smd_adjust_dt.html"><span class="doc">smd/adjust_dt</span></a> - calculate a new stable time increment for use with SMD integrators</p></li>
<li><p><a class="reference internal" href="fix_smd_integrate_tlsph.html"><span class="doc">smd/integrate_tlsph</span></a> - explicit time integration with total Lagrangian SPH pair style</p></li>
<li><p><a class="reference internal" href="fix_smd_integrate_ulsph.html"><span class="doc">smd/integrate_ulsph</span></a> - explicit time integration with updated Lagrangian SPH pair style</p></li>
<li><p><a class="reference internal" href="fix_smd_move_triangulated_surface.html"><span class="doc">smd/move_tri_surf</span></a> - update position and velocity near rigid surfaces using SPH integrators</p></li>
<li><p><a class="reference internal" href="fix_smd_setvel.html"><span class="doc">smd/setvel</span></a> - sets each velocity component, ignoring forces, for Smooth Mach Dynamics</p></li>
<li><p><a class="reference internal" href="fix_smd_wall_surface.html"><span class="doc">smd/wall_surface</span></a> - create a rigid wall with a triangulated surface for use in Smooth Mach Dynamics</p></li>
<li><p><a class="reference internal" href="fix_sph.html"><span class="doc">sph</span></a> - time integration for SPH/DPDE particles</p></li>
<li><p><a class="reference internal" href="fix_sph_stationary.html"><span class="doc">sph/stationary</span></a> - update energy and density but not position or velocity in Smooth Particle Hydrodynamics</p></li>
<li><p><a class="reference internal" href="fix_spring.html"><span class="doc">spring</span></a> - apply harmonic spring force to group of atoms</p></li>
<li><p><a class="reference internal" href="fix_spring_chunk.html"><span class="doc">spring/chunk</span></a> - apply harmonic spring force to each chunk of atoms</p></li>
<li><p><a class="reference internal" href="fix_spring_rg.html"><span class="doc">spring/rg</span></a> - spring on radius of gyration of group of atoms</p></li>
<li><p><a class="reference internal" href="fix_spring_self.html"><span class="doc">spring/self</span></a> - spring from each atom to its origin</p></li>
<li><p><a class="reference internal" href="fix_srd.html"><span class="doc">srd</span></a> - stochastic rotation dynamics (SRD)</p></li>
<li><p><a class="reference internal" href="fix_store_force.html"><span class="doc">store/force</span></a> - store force on each atom</p></li>
<li><p><a class="reference internal" href="fix_store_state.html"><span class="doc">store/state</span></a> - store attributes for each atom</p></li>
<li><p><a class="reference internal" href="fix_dpd_source.html"><span class="doc">tdpd/source</span></a> - add external concentration source</p></li>
<li><p><a class="reference internal" href="fix_temp_berendsen.html"><span class="doc">temp/berendsen</span></a> - temperature control by Berendsen thermostat</p></li>
<li><p><a class="reference internal" href="fix_temp_csvr.html"><span class="doc">temp/csld</span></a> - canonical sampling thermostat with Langevin dynamics</p></li>
<li><p><a class="reference internal" href="fix_temp_csvr.html"><span class="doc">temp/csvr</span></a> - canonical sampling thermostat with Hamiltonian dynamics</p></li>
<li><p><a class="reference internal" href="fix_temp_rescale.html"><span class="doc">temp/rescale</span></a> - temperature control by velocity rescaling</p></li>
<li><p><a class="reference internal" href="fix_temp_rescale_eff.html"><span class="doc">temp/rescale/eff</span></a> - temperature control by velocity rescaling in the electron force field model</p></li>
<li><p><a class="reference internal" href="fix_tfmc.html"><span class="doc">tfmc</span></a> - perform force-bias Monte Carlo with time-stamped method</p></li>
<li><p><a class="reference internal" href="fix_tgnh_drude.html"><span class="doc">tgnvt/drude</span></a> - NVT time integration for Drude polarizable model via temperature-grouped Nose-Hoover</p></li>
<li><p><a class="reference internal" href="fix_tgnh_drude.html"><span class="doc">tgnpt/drude</span></a> - NPT time integration for Drude polarizable model via temperature-grouped Nose-Hoover</p></li>
<li><p><a class="reference internal" href="fix_thermal_conductivity.html"><span class="doc">thermal/conductivity</span></a> - Mueller-Plathe kinetic energy exchange for thermal conductivity calculation</p></li>
<li><p><a class="reference internal" href="fix_ti_spring.html"><span class="doc">ti/spring</span></a> - perform thermodynamic integration between a solid and an Einstein crystal</p></li>
<li><p><a class="reference internal" href="fix_tmd.html"><span class="doc">tmd</span></a> - guide a group of atoms to a new configuration</p></li>
<li><p><a class="reference internal" href="fix_ttm.html"><span class="doc">ttm</span></a> - two-temperature model for electronic/atomic coupling (replicated grid)</p></li>
<li><p><a class="reference internal" href="fix_ttm.html"><span class="doc">ttm/grid</span></a> - two-temperature model for electronic/atomic coupling (distributed grid)</p></li>
<li><p><a class="reference internal" href="fix_ttm.html"><span class="doc">ttm/mod</span></a> - enhanced two-temperature model with additional options</p></li>
<li><p><a class="reference internal" href="fix_tune_kspace.html"><span class="doc">tune/kspace</span></a> - auto-tune <span class="math notranslate nohighlight">\(k\)</span>-space parameters</p></li>
<li><p><a class="reference internal" href="fix_vector.html"><span class="doc">vector</span></a> - accumulate a global vector every <em>N</em> timesteps</p></li>
<li><p><a class="reference internal" href="fix_viscosity.html"><span class="doc">viscosity</span></a> - Mueller-Plathe momentum exchange for viscosity calculation</p></li>
<li><p><a class="reference internal" href="fix_viscous.html"><span class="doc">viscous</span></a> - viscous damping for granular simulations</p></li>
<li><p><a class="reference internal" href="fix_viscous_sphere.html"><span class="doc">viscous/sphere</span></a> - viscous damping on angular velocity for granular simulations</p></li>
<li><p><a class="reference internal" href="fix_wall_body_polygon.html"><span class="doc">wall/body/polygon</span></a> - time integration for body particles of style <a class="reference internal" href="Howto_body.html"><span class="doc">rounded/polygon</span></a></p></li>
<li><p><a class="reference internal" href="fix_wall_body_polyhedron.html"><span class="doc">wall/body/polyhedron</span></a> - time integration for body particles of style <a class="reference internal" href="Howto_body.html"><span class="doc">rounded/polyhedron</span></a></p></li>
<li><p><a class="reference internal" href="fix_wall.html"><span class="doc">wall/colloid</span></a> - Lennard-Jones wall interacting with finite-size particles</p></li>
<li><p><a class="reference internal" href="fix_wall_ees.html"><span class="doc">wall/ees</span></a> - wall for ellipsoidal particles</p></li>
<li><p><a class="reference internal" href="fix_wall_flow.html"><span class="doc">wall/flow</span></a> - flow boundary conditions</p></li>
<li><p><a class="reference internal" href="fix_wall_gran.html"><span class="doc">wall/gran</span></a> - frictional wall(s) for granular simulations</p></li>
<li><p><a class="reference internal" href="fix_wall_gran_region.html"><span class="doc">wall/gran/region</span></a> - <a class="reference internal" href="fix_wall_region.html"><span class="doc">fix wall/region</span></a> equivalent for use with granular particles</p></li>
<li><p><a class="reference internal" href="fix_wall.html"><span class="doc">wall/harmonic</span></a> - harmonic spring wall</p></li>
<li><p><a class="reference internal" href="fix_wall.html"><span class="doc">wall/lj1043</span></a> - Lennard-Jones 1043 wall</p></li>
<li><p><a class="reference internal" href="fix_wall.html"><span class="doc">wall/lj126</span></a> - Lennard-Jones 126 wall</p></li>
<li><p><a class="reference internal" href="fix_wall.html"><span class="doc">wall/lj93</span></a> - Lennard-Jones 93 wall</p></li>
<li><p><a class="reference internal" href="fix_wall.html"><span class="doc">wall/lepton</span></a> - Custom Lepton expression wall</p></li>
<li><p><a class="reference internal" href="fix_wall.html"><span class="doc">wall/morse</span></a> - Morse potential wall</p></li>
<li><p><a class="reference internal" href="fix_wall_piston.html"><span class="doc">wall/piston</span></a> - moving reflective piston wall</p></li>
<li><p><a class="reference internal" href="fix_wall_reflect.html"><span class="doc">wall/reflect</span></a> - reflecting wall(s)</p></li>
<li><p><a class="reference internal" href="fix_wall_reflect_stochastic.html"><span class="doc">wall/reflect/stochastic</span></a> - reflecting wall(s) with finite temperature</p></li>
<li><p><a class="reference internal" href="fix_wall_region.html"><span class="doc">wall/region</span></a> - use region surface as wall</p></li>
<li><p><a class="reference internal" href="fix_wall_ees.html"><span class="doc">wall/region/ees</span></a> - use region surface as wall for ellipsoidal particles</p></li>
<li><p><a class="reference internal" href="fix_wall_srd.html"><span class="doc">wall/srd</span></a> - slip/no-slip wall for SRD particles</p></li>
<li><p><a class="reference internal" href="fix_wall.html"><span class="doc">wall/table</span></a> - Tabulated potential wall wall</p></li>
<li><p><a class="reference internal" href="fix_widom.html"><span class="doc">widom</span></a> - Widom insertions of atoms or molecules</p></li>
</ul>
</section>
<section id="restrictions">
<h2>Restrictions<a class="headerlink" href="#restrictions" title="Link to this heading"></a></h2>
<p>Some fix styles are part of specific packages. They are only enabled
if LAMMPS was built with that package. See the
<a class="reference internal" href="Build_package.html"><span class="doc">Build package</span></a> page for more info. The doc pages for
individual fixes tell if it is part of a package.</p>
</section>
<section id="related-commands">
<h2>Related commands<a class="headerlink" href="#related-commands" title="Link to this heading"></a></h2>
<p><a class="reference internal" href="unfix.html"><span class="doc">unfix</span></a>, <a class="reference internal" href="fix_modify.html"><span class="doc">fix_modify</span></a></p>
</section>
<section id="default">
<h2>Default<a class="headerlink" href="#default" title="Link to this heading"></a></h2>
<p>none</p>
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