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<title>atom_style command &mdash; LAMMPS documentation</title>
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<div class="lammps_version">Version: <b>19 Nov 2024</b></div>
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<p class="caption" role="heading"><span class="caption-text">User Guide</span></p>
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<li class="toctree-l1"><a class="reference internal" href="Intro.html">1. Introduction</a></li>
<li class="toctree-l1"><a class="reference internal" href="Install.html">2. Install LAMMPS</a></li>
<li class="toctree-l1"><a class="reference internal" href="Build.html">3. Build LAMMPS</a></li>
<li class="toctree-l1"><a class="reference internal" href="Run_head.html">4. Run LAMMPS</a></li>
<li class="toctree-l1"><a class="reference internal" href="Commands.html">5. Commands</a></li>
<li class="toctree-l1"><a class="reference internal" href="Packages.html">6. Optional packages</a></li>
<li class="toctree-l1"><a class="reference internal" href="Speed.html">7. Accelerate performance</a></li>
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<p class="caption" role="heading"><span class="caption-text">Programmer Guide</span></p>
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<li class="toctree-l1"><a class="reference internal" href="Library.html">1. LAMMPS Library Interfaces</a></li>
<li class="toctree-l1"><a class="reference internal" href="Python_head.html">2. Use Python with LAMMPS</a></li>
<li class="toctree-l1"><a class="reference internal" href="Modify.html">3. Modifying &amp; extending LAMMPS</a></li>
<li class="toctree-l1"><a class="reference internal" href="Developer.html">4. Information for Developers</a></li>
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<p class="caption" role="heading"><span class="caption-text">Command Reference</span></p>
<ul class="current">
<li class="toctree-l1 current"><a class="reference internal" href="commands_list.html">Commands</a><ul class="current">
<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>
<li class="toctree-l2"><a class="reference internal" href="angle_write.html">angle_write command</a></li>
<li class="toctree-l2"><a class="reference internal" href="atom_modify.html">atom_modify command</a></li>
<li class="toctree-l2 current"><a class="current reference internal" href="#">atom_style command</a><ul>
<li class="toctree-l3"><a class="reference internal" href="#syntax">Syntax</a></li>
<li class="toctree-l3"><a class="reference internal" href="#examples">Examples</a></li>
<li class="toctree-l3"><a class="reference internal" href="#description">Description</a></li>
<li class="toctree-l3"><a class="reference internal" href="#atom-style-attributes">Atom style attributes</a></li>
<li class="toctree-l3"><a class="reference internal" href="#particle-size-and-mass">Particle size and mass</a></li>
<li class="toctree-l3"><a class="reference internal" href="#additional-information-about-specific-atom-styles">Additional information about specific atom styles</a></li>
<li class="toctree-l3"><a class="reference internal" href="#restrictions">Restrictions</a></li>
<li class="toctree-l3"><a class="reference internal" href="#related-commands">Related commands</a></li>
<li class="toctree-l3"><a class="reference internal" href="#default">Default</a></li>
</ul>
</li>
<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>
<li class="toctree-l2"><a class="reference internal" href="bond_write.html">bond_write command</a></li>
<li class="toctree-l2"><a class="reference internal" href="boundary.html">boundary command</a></li>
<li class="toctree-l2"><a class="reference internal" href="change_box.html">change_box command</a></li>
<li class="toctree-l2"><a class="reference internal" href="clear.html">clear command</a></li>
<li class="toctree-l2"><a class="reference internal" href="comm_modify.html">comm_modify command</a></li>
<li class="toctree-l2"><a class="reference internal" href="comm_style.html">comm_style command</a></li>
<li class="toctree-l2"><a class="reference internal" href="compute.html">compute command</a></li>
<li class="toctree-l2"><a class="reference internal" href="compute_modify.html">compute_modify command</a></li>
<li class="toctree-l2"><a class="reference internal" href="create_atoms.html">create_atoms command</a></li>
<li class="toctree-l2"><a class="reference internal" href="create_bonds.html">create_bonds command</a></li>
<li class="toctree-l2"><a class="reference internal" href="create_box.html">create_box command</a></li>
<li class="toctree-l2"><a class="reference internal" href="delete_atoms.html">delete_atoms command</a></li>
<li class="toctree-l2"><a class="reference internal" href="delete_bonds.html">delete_bonds command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dielectric.html">dielectric command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_coeff.html">dihedral_coeff command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_style.html">dihedral_style command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dihedral_write.html">dihedral_write command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dimension.html">dimension command</a></li>
<li class="toctree-l2"><a class="reference internal" href="displace_atoms.html">displace_atoms command</a></li>
<li class="toctree-l2"><a class="reference internal" href="dynamical_matrix.html">dynamical_matrix command</a></li>
<li class="toctree-l2"><a class="reference internal" href="echo.html">echo command</a></li>
<li class="toctree-l2"><a class="reference internal" href="fix.html">fix command</a></li>
<li class="toctree-l2"><a class="reference internal" href="fix_modify.html">fix_modify command</a></li>
<li class="toctree-l2"><a class="reference internal" href="fitpod_command.html">fitpod command</a></li>
<li class="toctree-l2"><a class="reference internal" href="geturl.html">geturl command</a></li>
<li class="toctree-l2"><a class="reference internal" href="group.html">group command</a></li>
<li class="toctree-l2"><a class="reference internal" href="group2ndx.html">group2ndx command</a></li>
<li class="toctree-l2"><a class="reference internal" href="group2ndx.html#ndx2group-command">ndx2group command</a></li>
<li class="toctree-l2"><a class="reference internal" href="hyper.html">hyper command</a></li>
<li class="toctree-l2"><a class="reference internal" href="if.html">if command</a></li>
<li class="toctree-l2"><a class="reference internal" href="improper_coeff.html">improper_coeff command</a></li>
<li class="toctree-l2"><a class="reference internal" href="improper_style.html">improper_style command</a></li>
<li class="toctree-l2"><a class="reference internal" href="include.html">include command</a></li>
<li class="toctree-l2"><a class="reference internal" href="info.html">info command</a></li>
<li class="toctree-l2"><a class="reference internal" href="jump.html">jump command</a></li>
<li class="toctree-l2"><a class="reference internal" href="kim_commands.html">kim command</a></li>
<li class="toctree-l2"><a class="reference internal" href="kspace_modify.html">kspace_modify command</a></li>
<li class="toctree-l2"><a class="reference internal" href="kspace_style.html">kspace_style command</a></li>
<li class="toctree-l2"><a class="reference internal" href="label.html">label command</a></li>
<li class="toctree-l2"><a class="reference internal" href="labelmap.html">labelmap command</a></li>
<li class="toctree-l2"><a class="reference internal" href="lattice.html">lattice command</a></li>
<li class="toctree-l2"><a class="reference internal" href="log.html">log command</a></li>
<li class="toctree-l2"><a class="reference internal" href="mass.html">mass command</a></li>
<li class="toctree-l2"><a class="reference internal" href="mdi.html">mdi command</a></li>
<li class="toctree-l2"><a class="reference internal" href="min_modify.html">min_modify command</a></li>
<li class="toctree-l2"><a class="reference internal" href="min_spin.html">min_style spin command</a></li>
<li class="toctree-l2"><a class="reference internal" href="min_spin.html#min-style-spin-cg-command">min_style spin/cg command</a></li>
<li class="toctree-l2"><a class="reference internal" href="min_spin.html#min-style-spin-lbfgs-command">min_style spin/lbfgs command</a></li>
<li class="toctree-l2"><a class="reference internal" href="min_style.html">min_style cg command</a></li>
<li class="toctree-l2"><a class="reference internal" href="min_style.html#min-style-hftn-command">min_style hftn command</a></li>
<li class="toctree-l2"><a class="reference internal" href="min_style.html#min-style-sd-command">min_style sd command</a></li>
<li class="toctree-l2"><a class="reference internal" href="min_style.html#min-style-quickmin-command">min_style quickmin command</a></li>
<li class="toctree-l2"><a class="reference internal" href="min_style.html#min-style-fire-command">min_style fire command</a></li>
<li class="toctree-l2"><a class="reference internal" href="min_style.html#min-style-spin-command"><span class="xref std std-doc">min_style spin</span> command</a></li>
<li class="toctree-l2"><a class="reference internal" href="min_style.html#min-style-spin-cg-command"><span class="xref std std-doc">min_style spin/cg</span> command</a></li>
<li class="toctree-l2"><a class="reference internal" href="min_style.html#min-style-spin-lbfgs-command"><span class="xref std std-doc">min_style spin/lbfgs</span> command</a></li>
<li class="toctree-l2"><a class="reference internal" href="minimize.html">minimize command</a></li>
<li class="toctree-l2"><a class="reference internal" href="molecule.html">molecule command</a></li>
<li class="toctree-l2"><a class="reference internal" href="neb.html">neb command</a></li>
<li class="toctree-l2"><a class="reference internal" href="neb_spin.html">neb/spin command</a></li>
<li class="toctree-l2"><a class="reference internal" href="neigh_modify.html">neigh_modify command</a></li>
<li class="toctree-l2"><a class="reference internal" href="neighbor.html">neighbor command</a></li>
<li class="toctree-l2"><a class="reference internal" href="newton.html">newton command</a></li>
<li class="toctree-l2"><a class="reference internal" href="next.html">next command</a></li>
<li class="toctree-l2"><a class="reference internal" href="package.html">package command</a></li>
<li class="toctree-l2"><a class="reference internal" href="pair_coeff.html">pair_coeff command</a></li>
<li class="toctree-l2"><a class="reference internal" href="pair_modify.html">pair_modify command</a></li>
<li class="toctree-l2"><a class="reference internal" href="pair_style.html">pair_style command</a></li>
<li class="toctree-l2"><a class="reference internal" href="pair_write.html">pair_write command</a></li>
<li class="toctree-l2"><a class="reference internal" href="partition.html">partition command</a></li>
<li class="toctree-l2"><a class="reference internal" href="plugin.html">plugin command</a></li>
<li class="toctree-l2"><a class="reference internal" href="prd.html">prd command</a></li>
<li class="toctree-l2"><a class="reference internal" href="print.html">print command</a></li>
<li class="toctree-l2"><a class="reference internal" href="processors.html">processors command</a></li>
<li class="toctree-l2"><a class="reference internal" href="python.html">python command</a></li>
<li class="toctree-l2"><a class="reference internal" href="quit.html">quit command</a></li>
<li class="toctree-l2"><a class="reference internal" href="read_data.html">read_data command</a></li>
<li class="toctree-l2"><a class="reference internal" href="read_dump.html">read_dump command</a></li>
<li class="toctree-l2"><a class="reference internal" href="read_restart.html">read_restart command</a></li>
<li class="toctree-l2"><a class="reference internal" href="region.html">region command</a></li>
<li class="toctree-l2"><a class="reference internal" href="replicate.html">replicate command</a></li>
<li class="toctree-l2"><a class="reference internal" href="rerun.html">rerun command</a></li>
<li class="toctree-l2"><a class="reference internal" href="reset_atoms.html">reset_atoms command</a></li>
<li class="toctree-l2"><a class="reference internal" href="reset_timestep.html">reset_timestep command</a></li>
<li class="toctree-l2"><a class="reference internal" href="restart.html">restart command</a></li>
<li class="toctree-l2"><a class="reference internal" href="run.html">run command</a></li>
<li class="toctree-l2"><a class="reference internal" href="run_style.html">run_style command</a></li>
<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>
<li class="toctree-l2"><a class="reference internal" href="temper.html">temper command</a></li>
<li class="toctree-l2"><a class="reference internal" href="temper_grem.html">temper/grem command</a></li>
<li class="toctree-l2"><a class="reference internal" href="temper_npt.html">temper/npt command</a></li>
<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>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="fixes.html">Fix Styles</a></li>
<li class="toctree-l1"><a class="reference internal" href="computes.html">Compute Styles</a></li>
<li class="toctree-l1"><a class="reference internal" href="pairs.html">Pair Styles</a></li>
<li class="toctree-l1"><a class="reference internal" href="bonds.html">Bond Styles</a></li>
<li class="toctree-l1"><a class="reference internal" href="angles.html">Angle Styles</a></li>
<li class="toctree-l1"><a class="reference internal" href="dihedrals.html">Dihedral Styles</a></li>
<li class="toctree-l1"><a class="reference internal" href="impropers.html">Improper Styles</a></li>
<li class="toctree-l1"><a class="reference internal" href="dumps.html">Dump Styles</a></li>
<li class="toctree-l1"><a class="reference internal" href="fix_modify_atc_commands.html">fix_modify AtC commands</a></li>
<li class="toctree-l1"><a class="reference internal" href="Bibliography.html">Bibliography</a></li>
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<p><span class="math notranslate nohighlight">\(\renewcommand{\AA}{\text{Å}}\)</span></p>
<section id="atom-style-command">
<span id="index-0"></span><h1>atom_style command<a class="headerlink" href="#atom-style-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">atom_style</span><span class="w"> </span><span class="n">style</span><span class="w"> </span><span class="n">args</span>
</pre></div>
</div>
<ul>
<li><p>style = <em>amoeba</em> or <em>angle</em> or <em>atomic</em> or <em>body</em> or <em>bond</em> or <em>charge</em> or <em>dielectric</em> or <em>dipole</em> or <em>dpd</em> or <em>edpd</em> or <em>electron</em> or <em>ellipsoid</em> or <em>full</em> or <em>line</em> or <em>mdpd</em> or <em>molecular</em> or <em>oxdna</em> or <em>peri</em> or <em>smd</em> or <em>sph</em> or <em>sphere</em> or <em>bpm/sphere</em> or <em>spin</em> or <em>tdpd</em> or <em>tri</em> or <em>template</em> or <em>wavepacket</em> or <em>hybrid</em></p>
<pre class="literal-block">args = none for any style except the following
<em>body</em> args = bstyle bstyle-args
bstyle = style of body particles
bstyle-args = additional arguments specific to the bstyle
see the <a class="reference internal" href="Howto_body.html"><span class="doc">Howto body</span></a> doc
page for details
<em>sphere</em> arg = 0/1 (optional) for static/dynamic particle radii
<em>bpm/sphere</em> arg = 0/1 (optional) for static/dynamic particle radii
<em>tdpd</em> arg = Nspecies
Nspecies = # of chemical species
<em>template</em> arg = template-ID
template-ID = ID of molecule template specified in a separate <a class="reference internal" href="molecule.html"><span class="doc">molecule</span></a> command
<em>hybrid</em> args = list of one or more sub-styles, each with their args</pre>
</li>
<li><p>accelerated styles (with same args) = <em>angle/kk</em> or <em>atomic/kk</em> or <em>bond/kk</em> or <em>charge/kk</em> or <em>full/kk</em> or <em>molecular/kk</em> or <em>spin/kk</em></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">atom_style</span><span class="w"> </span><span class="n">atomic</span>
<span class="k">atom_style</span><span class="w"> </span><span class="n">bond</span>
<span class="k">atom_style</span><span class="w"> </span><span class="n">full</span>
<span class="k">atom_style</span><span class="w"> </span><span class="n">body</span><span class="w"> </span><span class="n">nparticle</span><span class="w"> </span><span class="m">2</span><span class="w"> </span><span class="m">10</span>
<span class="k">atom_style</span><span class="w"> </span><span class="n">hybrid</span><span class="w"> </span><span class="n">charge</span><span class="w"> </span><span class="n">bond</span>
<span class="k">atom_style</span><span class="w"> </span><span class="n">hybrid</span><span class="w"> </span><span class="n">charge</span><span class="w"> </span><span class="n">body</span><span class="w"> </span><span class="n">nparticle</span><span class="w"> </span><span class="m">2</span><span class="w"> </span><span class="m">5</span>
<span class="k">atom_style</span><span class="w"> </span><span class="n">spin</span>
<span class="k">atom_style</span><span class="w"> </span><span class="n">template</span><span class="w"> </span><span class="n">myMols</span>
<span class="k">atom_style</span><span class="w"> </span><span class="n">hybrid</span><span class="w"> </span><span class="n">template</span><span class="w"> </span><span class="n">twomols</span><span class="w"> </span><span class="n">charge</span>
<span class="k">atom_style</span><span class="w"> </span><span class="n">tdpd</span><span class="w"> </span><span class="m">2</span>
</pre></div>
</div>
</section>
<section id="description">
<h2>Description<a class="headerlink" href="#description" title="Link to this heading"></a></h2>
<p>The <em>atom_style</em> command selects which per-atom attributes are
associated with atoms in a LAMMPS simulation and thus stored and
communicated with those atoms as well as read from and stored in data
and restart files. Different models (e.g. <a class="reference internal" href="pair_style.html"><span class="doc">pair styles</span></a>) require access to specific per-atom attributes and thus
require a specific atom style. For example, to compute Coulomb
interactions, the atom must have a “charge” (aka “q”) attribute.</p>
<p>A number of distinct atom styles exist that combine attributes. Some
atom styles are a superset of other atom styles. Further attributes
may be added to atoms either via using a hybrid style which provides a
union of the attributes of the sub-styles, or via the <a class="reference internal" href="fix_property_atom.html"><span class="doc">fix
property/atom</span></a> command. The <em>atom_style</em> command
must be used before a simulation is setup via a <a class="reference internal" href="read_data.html"><span class="doc">read_data</span></a>, <a class="reference internal" href="read_restart.html"><span class="doc">read_restart</span></a>, or <a class="reference internal" href="create_box.html"><span class="doc">create_box</span></a> command.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Many of the atom styles discussed here are only enabled if LAMMPS was
built with a specific package, as listed below in the Restrictions
section.</p>
</div>
<p>Once a style is selected and the simulation box defined, it cannot be
changed but only augmented with the <a class="reference internal" href="fix_property_atom.html"><span class="doc">fix property/atom</span></a> command. So one should select an atom style
general enough to encompass all attributes required. E.g. with atom
style <em>bond</em>, it is not possible to define angles and use angle styles.</p>
<p>It is OK to use a style more general than needed, though it may be
slightly inefficient because it will allocate and communicate
additional unused data.</p>
</section>
<section id="atom-style-attributes">
<h2>Atom style attributes<a class="headerlink" href="#atom-style-attributes" title="Link to this heading"></a></h2>
<p>The atom style <em>atomic</em> has the minimum subset of per-atom attributes
and is also the default setting. It encompasses the following per-atom
attributes (name of the vector or array in the <a class="reference internal" href="Classes_atom.html"><span class="doc">Atom class</span></a> is given in parenthesis): atom-ID (tag), type (type),
position (x), velocities (v), forces (f), image flags (image), group
membership (mask). Since all atom styles are a superset of atom style
<em>atomic</em>, they all include these attributes.</p>
<p>This table lists all the available atom styles, which attributes they
provide, which <a class="reference internal" href="Packages.html"><span class="doc">package</span></a> is required to use them, and
what the typical applications are that use them. See the
<a class="reference internal" href="read_data.html"><span class="doc">read_data</span></a>, <a class="reference internal" href="create_atoms.html"><span class="doc">create_atoms</span></a>, and
<a class="reference internal" href="set.html"><span class="doc">set</span></a> commands for details on how to set these various
quantities. More information about many of the styles is provided in
the Additional Information section below.</p>
<table class="docutils align-default">
<colgroup>
<col style="width: 13.3%" />
<col style="width: 31.1%" />
<col style="width: 20.0%" />
<col style="width: 35.6%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head"><p>Atom style</p></th>
<th class="head"><p>Attributes</p></th>
<th class="head"><p>Required package</p></th>
<th class="head"><p>Applications</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p><em>amoeba</em></p></td>
<td><p><em>full</em> + “1-5 special neighbor data”</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-amoeba"><span class="std std-ref">AMOEBA</span></a></p></td>
<td><p>AMOEBA/HIPPO force fields</p></td>
</tr>
<tr class="row-odd"><td><p><em>angle</em></p></td>
<td><p><em>bond</em> + “angle data”</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-molecule"><span class="std std-ref">MOLECULE</span></a></p></td>
<td><p>bead-spring polymers with stiffness</p></td>
</tr>
<tr class="row-even"><td><p><em>atomic</em></p></td>
<td><p>tag, type, x, v, f, image, mask</p></td>
<td></td>
<td><p>atomic liquids, solids, metals</p></td>
</tr>
<tr class="row-odd"><td><p><em>body</em></p></td>
<td><p><em>atomic</em> + radius, rmass, angmom, torque, body</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-body"><span class="std std-ref">BODY</span></a></p></td>
<td><p>arbitrary bodies, see <a class="reference internal" href="Howto_body.html"><span class="doc">body howto</span></a></p></td>
</tr>
<tr class="row-even"><td><p><em>bond</em></p></td>
<td><p><em>atomic</em> + molecule, nspecial, special + “bond data”</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-molecule"><span class="std std-ref">MOLECULE</span></a></p></td>
<td><p>bead-spring polymers</p></td>
</tr>
<tr class="row-odd"><td><p><em>bpm/sphere</em></p></td>
<td><p><em>bond</em> + radius, rmass, omega, torque, quat</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-bpm"><span class="std std-ref">BPM</span></a></p></td>
<td><p>granular bonded particle models, see <a class="reference internal" href="Howto_bpm.html"><span class="doc">BPM howto</span></a></p></td>
</tr>
<tr class="row-even"><td><p><em>charge</em></p></td>
<td><p><em>atomic</em> + q</p></td>
<td></td>
<td><p>atomic systems with charges</p></td>
</tr>
<tr class="row-odd"><td><p><em>dielectric</em></p></td>
<td><p><em>full</em> + mu, area, ed, em, epsilon, curvature, q_scaled</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-dielectric"><span class="std std-ref">DIELECTRIC</span></a></p></td>
<td><p>systems with surface polarization</p></td>
</tr>
<tr class="row-even"><td><p><em>dipole</em></p></td>
<td><p><em>charge</em> + mu</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-dipole"><span class="std std-ref">DIPOLE</span></a></p></td>
<td><p>atomic systems with charges and point dipoles</p></td>
</tr>
<tr class="row-odd"><td><p><em>dpd</em></p></td>
<td><p><em>atomic</em> + rho + “reactive DPD data”</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-dpd-react"><span class="std std-ref">DPD-REACT</span></a></p></td>
<td><p>reactive DPD</p></td>
</tr>
<tr class="row-even"><td><p><em>edpd</em></p></td>
<td><p><em>atomic</em> + “eDPD data”</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-dpd-meso"><span class="std std-ref">DPD-MESO</span></a></p></td>
<td><p>Energy conservative DPD (eDPD)</p></td>
</tr>
<tr class="row-odd"><td><p><em>electron</em></p></td>
<td><p><em>charge</em> + espin, eradius, ervel, erforce</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-eff"><span class="std std-ref">EFF</span></a></p></td>
<td><p>Electron force field systems</p></td>
</tr>
<tr class="row-even"><td><p><em>ellipsoid</em></p></td>
<td><p><em>atomic</em> + rmass, angmom, torque, ellipsoid</p></td>
<td></td>
<td><p>aspherical particles</p></td>
</tr>
<tr class="row-odd"><td><p><em>full</em></p></td>
<td><p><em>molecular</em> + q</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-molecule"><span class="std std-ref">MOLECULE</span></a></p></td>
<td><p>molecular force fields</p></td>
</tr>
<tr class="row-even"><td><p><em>line</em></p></td>
<td><p><em>atomic</em> + molecule, radius, rmass, omega, torque, line</p></td>
<td></td>
<td><p>2-d rigid body particles</p></td>
</tr>
<tr class="row-odd"><td><p><em>mdpd</em></p></td>
<td><p><em>atomic</em> + rho, drho, vest</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-dpd-meso"><span class="std std-ref">DPD-MESO</span></a></p></td>
<td><p>Many-body DPD (mDPD)</p></td>
</tr>
<tr class="row-even"><td><p><em>molecular</em></p></td>
<td><p><em>angle</em> + “dihedral and improper data”</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-molecule"><span class="std std-ref">MOLECULE</span></a></p></td>
<td><p>apolar and uncharged molecules</p></td>
</tr>
<tr class="row-odd"><td><p><em>oxdna</em></p></td>
<td><p><em>atomic</em> + id5p</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-cg-dna"><span class="std std-ref">CG-DNA</span></a></p></td>
<td><p>coarse-grained DNA and RNA models</p></td>
</tr>
<tr class="row-even"><td><p><em>peri</em></p></td>
<td><p><em>atomic</em> + rmass, vfrac, s0, x0</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-peri"><span class="std std-ref">PERI</span></a></p></td>
<td><p>mesoscopic Peridynamics models</p></td>
</tr>
<tr class="row-odd"><td><p><em>smd</em></p></td>
<td><p><em>atomic</em> + molecule, radius, rmass + “smd data”</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-machdyn"><span class="std std-ref">MACHDYN</span></a></p></td>
<td><p>Smooth Mach Dynamics models</p></td>
</tr>
<tr class="row-even"><td><p><em>rheo</em></p></td>
<td><p><em>atomic</em> + rho, status</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-rheo"><span class="std std-ref">RHEO</span></a></p></td>
<td><p>solid and fluid RHEO particles</p></td>
</tr>
<tr class="row-odd"><td><p><em>rheo/thermal</em></p></td>
<td><p><em>atomic</em> + rho, status, energy, temperature</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-rheo"><span class="std std-ref">RHEO</span></a></p></td>
<td><p>RHEO particles with temperature</p></td>
</tr>
<tr class="row-even"><td><p><em>sph</em></p></td>
<td><p><em>atomic</em> + “sph data”</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-sph"><span class="std std-ref">SPH</span></a></p></td>
<td><p>Smoothed particle hydrodynamics models</p></td>
</tr>
<tr class="row-odd"><td><p><em>sphere</em></p></td>
<td><p><em>atomic</em> + radius, rmass, omega, torque</p></td>
<td></td>
<td><p>finite size spherical particles, e.g. granular models</p></td>
</tr>
<tr class="row-even"><td><p><em>spin</em></p></td>
<td><p><em>atomic</em> + “magnetic moment data”</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-spin"><span class="std std-ref">SPIN</span></a></p></td>
<td><p>magnetic particles</p></td>
</tr>
<tr class="row-odd"><td><p><em>tdpd</em></p></td>
<td><p><em>atomic</em> + cc, cc_flux, vest</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-dpd-meso"><span class="std std-ref">DPD-MESO</span></a></p></td>
<td><p>Transport DPD (tDPD)</p></td>
</tr>
<tr class="row-even"><td><p><em>template</em></p></td>
<td><p><em>atomic</em> + molecule, molindex, molatom</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-molecule"><span class="std std-ref">MOLECULE</span></a></p></td>
<td><p>molecular systems where attributes are taken from <a class="reference internal" href="molecule.html"><span class="doc">molecule files</span></a></p></td>
</tr>
<tr class="row-odd"><td><p><em>tri</em></p></td>
<td><p><em>sphere</em> + molecule, angmom, tri</p></td>
<td></td>
<td><p>3-d triangulated rigid body LJ particles</p></td>
</tr>
<tr class="row-even"><td><p><em>wavepacket</em></p></td>
<td><p><em>charge</em> + “wavepacket data”</p></td>
<td><p><a class="reference internal" href="Packages_details.html#pkg-awpmd"><span class="std std-ref">AWPMD</span></a></p></td>
<td><p>Antisymmetrized wave packet MD</p></td>
</tr>
</tbody>
</table>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>It is possible to add some attributes, such as a molecule ID and
charge, to atom styles that do not have them built in using the
<a class="reference internal" href="fix_property_atom.html"><span class="doc">fix property/atom</span></a> command. This command
also allows new custom-named attributes consisting of extra integer
or floating-point values or vectors to be added to atoms. See the
<a class="reference internal" href="fix_property_atom.html"><span class="doc">fix property/atom</span></a> page for examples of
cases where this is useful and details on how to initialize,
access, and output these custom values.</p>
</div>
</section>
<hr class="docutils" />
<section id="particle-size-and-mass">
<h2>Particle size and mass<a class="headerlink" href="#particle-size-and-mass" title="Link to this heading"></a></h2>
<p>All of the atom styles define point particles unless they (1) define
finite-size spherical particles via the <em>radius</em> attribute, or (2)
define finite-size aspherical particles (e.g. the <em>body</em>, <em>ellipsoid</em>,
<em>line</em>, and <em>tri</em> styles). Most of these styles can also be used with
mixtures of point and finite-size particles.</p>
<p>Note that the <em>radius</em> property may need to be provided as a
<em>diameter</em> (e.g. in <a class="reference internal" href="molecule.html"><span class="doc">molecule files</span></a> or <a class="reference internal" href="read_data.html"><span class="doc">data
files</span></a>). See the <a class="reference internal" href="Howto_spherical.html"><span class="doc">Howto spherical</span></a>
page for an overview of using finite-size spherical and aspherical
particle models with LAMMPS.</p>
<p>Unless an atom style defines the per-atom <em>rmass</em> attribute, particle
masses are defined on a per-type basis, using the <a class="reference internal" href="mass.html"><span class="doc">mass</span></a>
command. This means each particles mass is indexed by its atom
<em>type</em>.</p>
<p>A few styles define the per-atom <em>rmass</em> attribute which can also be
added using the <a class="reference internal" href="fix_property_atom.html"><span class="doc">fix property/atom</span></a> command.
In this case each particle stores its own mass. Atom styles that have
a per-atom rmass may define it indirectly through setting particle
diameter and density on a per-particle basis. If both per-type mass
and per-atom <em>rmass</em> are defined (e.g. in a hybrid style), the
per-atom mass will take precedence in any operation which which works
with both flavors of mass.</p>
</section>
<hr class="docutils" />
<section id="additional-information-about-specific-atom-styles">
<h2>Additional information about specific atom styles<a class="headerlink" href="#additional-information-about-specific-atom-styles" title="Link to this heading"></a></h2>
<p>For the <em>body</em> style, the particles are arbitrary bodies with internal
attributes defined by the “style” of the bodies, which is specified by
the <em>bstyle</em> argument. Body particles can represent complex entities,
such as surface meshes of discrete points, collections of
sub-particles, deformable objects, etc.</p>
<p>The <a class="reference internal" href="Howto_body.html"><span class="doc">Howto body</span></a> page describes the body styles
LAMMPS currently supports, and provides more details as to the kind of
body particles they represent. For all styles, each body particle
stores moments of inertia and a quaternion 4-vector, so that its
orientation and position can be time integrated due to forces and
torques.</p>
<p>Note that there may be additional arguments required along with the
<em>bstyle</em> specification, in the atom_style body command. These
arguments are described on the <a class="reference internal" href="Howto_body.html"><span class="doc">Howto body</span></a> doc page.</p>
<p>For the <em>dielectric</em> style, each particle can be either a physical
particle (e.g. an ion), or an interface particle representing a
boundary element between two regions of different dielectric
constant. For interface particles, in addition to the properties
associated with atom_style full, each particle also should be assigned
a unit dipole vector (mu) representing the direction of the induced
dipole moment at each interface particle, an area (area/patch), the
difference and mean of the dielectric constants of two sides of the
interface along the direction of the normal vector (ed and em), the
local dielectric constant at the boundary element (epsilon), and a
mean local curvature (curv). Physical particles must be assigned
these values, as well, but only their local dielectric constants will
be used; see documentation for associated <a class="reference internal" href="pair_dielectric.html"><span class="doc">pair styles</span></a> and <a class="reference internal" href="fix_polarize.html"><span class="doc">fixes</span></a>. The distinction
between the physical and interface particles is only meaningful when
<a class="reference internal" href="fix_polarize.html"><span class="doc">fix polarize</span></a> commands are applied to the
interface particles. This style is part of the DIELECTRIC package.</p>
<p>For the <em>dipole</em> style, a point dipole vector mu is defined for each
point particle. Note that if you wish the particles to be finite-size
spheres as in a Stockmayer potential for a dipolar fluid, so that the
particles can rotate due to dipole-dipole interactions, then you need
to use the command <cite>atom_style hybrid sphere dipole</cite>, which will
assign both a diameter and dipole moment to each particle. This also
requires using an integrator with a “/sphere” suffix like <a class="reference internal" href="fix_nve_sphere.html"><span class="doc">fix
nve/sphere</span></a> or <a class="reference internal" href="fix_nvt_sphere.html"><span class="doc">fix nvt/sphere</span></a>
and the “update dipole” or “update dlm” parameters to the fix
commands.</p>
<p>The <em>dpd</em> style is for reactive dissipative particle dynamics (DPD)
particles. Note that it is part of the DPD-REACT package, and is not
required for use with the <a class="reference internal" href="pair_dpd.html"><span class="doc">pair_style dpd or dpd/stat</span></a>
commands, which only require the attributes from atom_style <em>atomic</em>.
Atom_style <em>dpd</em> extends DPD particle properties with internal
temperature (dpdTheta), internal conductive energy (uCond), internal
mechanical energy (uMech), and internal chemical energy (uChem).</p>
<p>The <em>edpd</em> style is for energy-conserving dissipative particle
dynamics (eDPD) particles which store a temperature (edpd_temp), and
heat capacity (edpd_cv).</p>
<p>For the <em>electron</em> style, the particles representing electrons are 3d
Gaussians with a specified position and bandwidth or uncertainty in
position, which is represented by the eradius = electron size.</p>
<p>For the <em>ellipsoid</em> style, particles can be ellipsoids which each
stores a shape vector with the 3 diameters of the ellipsoid and a
quaternion 4-vector with its orientation. Each particle stores a flag
in the ellipsoid vector which indicates whether it is an ellipsoid (1)
or a point particle (0).</p>
<p>For the <em>line</em> style, particles can be are idealized line segments
which store a per-particle mass and length and orientation (i.e. the
end points of the line segment). Each particle stores a flag in the
line vector which indicates whether it is a line segment (1) or a
point particle (0).</p>
<p>The <em>mdpd</em> style is for many-body dissipative particle dynamics (mDPD)
particles which store a density (rho) for considering density-dependent
many-body interactions.</p>
<p>The <em>oxdna</em> style is for coarse-grained nucleotides and stores the
3-to-5 polarity of the nucleotide strand, which is set through
the bond topology in the data file. The first (second) atom in a
bond definition is understood to point towards the 3-end (5-end)
of the strand.</p>
<p>For the <em>peri</em> style, the particles are spherical and each stores a
per-particle mass and volume.</p>
<p>The <em>smd</em> style is for Smooth Particle Mach dynamics. Both fluids and
solids can be modeled. Particles store the mass and volume of an
integration point, a kernel diameter used for calculating the field
variables (e.g. stress and deformation) and a contact radius for
calculating repulsive forces which prevent individual physical bodies
from penetrating each other.</p>
<p>The <em>sph</em> style is for smoothed particle hydrodynamics (SPH) particles
which store a density (rho), energy (esph), and heat capacity (cv).</p>
<p>For the <em>spin</em> style, a magnetic spin is associated with each atom.
Those spins have a norm (their magnetic moment) and a direction.</p>
<p>The <em>tdpd</em> style is for transport dissipative particle dynamics (tDPD)
particles which store a set of chemical concentration. An integer
“cc_species” is required to specify the number of chemical species
involved in a tDPD system.</p>
<p>The <em>wavepacket</em> style is similar to the <em>electron</em> style, but the
electrons may consist of several Gaussian wave packets, summed up with
coefficients cs= (cs_re,cs_im). Each of the wave packets is treated
as a separate particle in LAMMPS, wave packets belonging to the same
electron must have identical <em>etag</em> values.</p>
<p>The <em>sphere</em> and <em>bpm/sphere</em> styles allow particles to be either point
particles or finite-size particles. If the <em>radius</em> attribute is &gt;
0.0, the particle is a finite-size sphere. If the diameter = 0.0, it
is a point particle. Note that by using the <em>disc</em> keyword with the
<a class="reference internal" href="fix_nve_sphere.html"><span class="doc">fix nve/sphere</span></a>, <a class="reference internal" href="fix_nvt_sphere.html"><span class="doc">fix nvt/sphere</span></a>, <a class="reference internal" href="fix_nph_sphere.html"><span class="doc">fix nph/sphere</span></a>, <a class="reference internal" href="fix_npt_sphere.html"><span class="doc">fix
npt/sphere</span></a> commands for the <em>sphere</em> style, spheres
can be effectively treated as 2d discs for a 2d simulation if desired.
See also the <a class="reference internal" href="set.html"><span class="doc">set density/disc</span></a> command. These styles also
take an optional 0 or 1 argument. A value of 0 means the radius of
each sphere is constant for the duration of the simulation (this is
the default). A value of 1 means the radii may vary dynamically
during the simulation, e.g. due to use of the <a class="reference internal" href="fix_adapt.html"><span class="doc">fix adapt</span></a> command.</p>
<p>The <em>template</em> style allows molecular topology (bonds,angles,etc) to be
defined via a molecule template using the <a class="reference internal" href="molecule.html"><span class="doc">molecule</span></a>
command. The template stores one or more molecules with a single copy
of the topology info (bonds,angles,etc) of each. Individual atoms only
store a template index and template atom to identify which molecule and
which atom-within-the-molecule they represent. Using the <em>template</em>
style instead of the <em>bond</em>, <em>angle</em>, <em>molecular</em> styles can save memory
for systems comprised of a large number of small molecules, all of a
single type (or small number of types). See the paper by Grime and
Voth, in <a class="reference internal" href="#grime"><span class="std std-ref">(Grime)</span></a>, for examples of how this can be
advantageous for large-scale coarse-grained systems. The
<code class="docutils literal notranslate"><span class="pre">examples/template</span></code> directory has a few demo inputs and examples
showing the use of the <em>template</em> atom style versus <em>molecular</em>.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>When using the <em>template</em> style with a <a class="reference internal" href="molecule.html"><span class="doc">molecule template</span></a> that contains multiple molecules, you should ensure the
atom types, bond types, angle_types, etc in all the molecules are
consistent. E.g. if one molecule represents H2O and another CO2,
then you probably do not want each molecule file to define two atom
types and a single bond type, because they will conflict with each
other when a mixture system of H2O and CO2 molecules is defined,
e.g. by the <a class="reference internal" href="read_data.html"><span class="doc">read_data</span></a> command. Rather the H2O
molecule should define atom types 1 and 2, and bond type 1. And
the CO2 molecule should define atom types 3 and 4 (or atom types 3
and 2 if a single oxygen type is desired), and bond type 2.</p>
</div>
<p>For the <em>tri</em> style, particles can be planar triangles which each
stores a per-particle mass and size and orientation (i.e. the corner
points of the triangle). Each particle stores a flag in the tri
vector which indicates whether it is a triangle (1) or a point
particle (0).</p>
<hr class="docutils" />
<p>Typically, simulations require only a single (non-hybrid) atom style.
If some atoms in the simulation do not have all the properties defined
by a particular style, use the simplest style that defines all the
needed properties by any atom. For example, if some atoms in a
simulation are charged, but others are not, use the <em>charge</em> style.
If some atoms have bonds, but others do not, use the <em>bond</em> style.</p>
<p>The only scenario where the <em>hybrid</em> style is needed is if there is no
single style which defines all needed properties of all atoms. For
example, as mentioned above, if you want dipolar particles which will
rotate due to torque, you need to use “atom_style hybrid sphere
dipole”. When a hybrid style is used, atoms store and communicate the
union of all quantities implied by the individual styles.</p>
<p>When using the <em>hybrid</em> style, you cannot combine the <em>template</em> style
with another molecular style that stores bond, angle, etc info on a
per-atom basis.</p>
<p>LAMMPS can be extended with new atom styles as well as new body styles;
see the corresponding manual page on <a class="reference internal" href="Modify_atom.html"><span class="doc">modifying &amp; extending LAMMPS</span></a>.</p>
<hr class="docutils" />
<p>Styles with a <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 on the <a class="reference internal" href="Speed_packages.html"><span class="doc">Accelerator packages</span></a>
page. 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 GPU, INTEL, KOKKOS,
OPENMP, and OPT packages, respectively. They are only enabled if
LAMMPS was built with those packages. See the <a class="reference internal" href="Build_package.html"><span class="doc">Build package</span></a> page 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="Run_options.html"><span class="doc">-suffix command-line switch</span></a> when you invoke LAMMPS, or you can use the
<a class="reference internal" href="suffix.html"><span class="doc">suffix</span></a> command in your input script.</p>
<p>See the <a class="reference internal" href="Speed_packages.html"><span class="doc">Accelerator packages</span></a> page for more
instructions on how to use the accelerated styles effectively.</p>
</section>
<hr class="docutils" />
<section id="restrictions">
<h2>Restrictions<a class="headerlink" href="#restrictions" title="Link to this heading"></a></h2>
<p>This command cannot be used after the simulation box is defined by a
<a class="reference internal" href="read_data.html"><span class="doc">read_data</span></a> or <a class="reference internal" href="create_box.html"><span class="doc">create_box</span></a> command.</p>
<p>Many of the styles listed above are only enabled if LAMMPS was built
with a specific package, as listed below. See the <a class="reference internal" href="Build_package.html"><span class="doc">Build package</span></a> page for more info. The table above lists which package
is required for individual atom styles.</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="read_data.html"><span class="doc">read_data</span></a>, <a class="reference internal" href="pair_style.html"><span class="doc">pair_style</span></a>,
<a class="reference internal" href="fix_property_atom.html"><span class="doc">fix property/atom</span></a>, <a class="reference internal" href="set.html"><span class="doc">set</span></a></p>
</section>
<section id="default">
<h2>Default<a class="headerlink" href="#default" title="Link to this heading"></a></h2>
<p>The default atom style is <em>atomic</em>. If atom_style <em>sphere</em> or
<em>bpm/sphere</em> is used, its default argument is 0.</p>
<hr class="docutils" />
<p id="grime"><strong>(Grime)</strong> Grime and Voth, to appear in J Chem Theory &amp; Computation
(2014).</p>
</section>
</section>
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