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<title>pair_style zbl command &mdash; LAMMPS 15 Dec 2015 documentation</title>
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<div class="section" id="pair-style-zbl-command">
<span id="index-0"></span><h1>pair_style zbl command<a class="headerlink" href="#pair-style-zbl-command" title="Permalink to this headline">¶</a></h1>
</div>
<div class="section" id="pair-style-zbl-gpu-command">
<h1>pair_style zbl/gpu command<a class="headerlink" href="#pair-style-zbl-gpu-command" title="Permalink to this headline">¶</a></h1>
</div>
<div class="section" id="pair-style-zbl-omp-command">
<h1>pair_style zbl/omp command<a class="headerlink" href="#pair-style-zbl-omp-command" title="Permalink to this headline">¶</a></h1>
<div class="section" id="syntax">
<h2>Syntax<a class="headerlink" href="#syntax" title="Permalink to this headline">¶</a></h2>
<div class="highlight-python"><div class="highlight"><pre>pair_style zbl inner outer
</pre></div>
</div>
<ul class="simple">
<li>inner = distance where switching function begins</li>
<li>outer = global cutoff for ZBL interaction</li>
</ul>
</div>
<div class="section" id="examples">
<h2>Examples<a class="headerlink" href="#examples" title="Permalink to this headline">¶</a></h2>
<div class="highlight-python"><div class="highlight"><pre>pair_style zbl 3.0 4.0
pair_coeff * * 73.0 73.0
pair_coeff 1 1 14.0 14.0
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
<p>Style <em>zbl</em> computes the Ziegler-Biersack-Littmark (ZBL) screened nuclear
repulsion for describing high-energy collisions between atoms.
<a class="reference internal" href="#ziegler"><span>(Ziegler)</span></a>. It includes an additional switching function
that ramps the energy, force, and curvature smoothly to zero
between an inner and outer cutoff. The potential
energy due to a pair of atoms at a distance r_ij is given by:</p>
<img alt="_images/pair_zbl.jpg" class="align-center" src="_images/pair_zbl.jpg" />
<p>where e is the electron charge, epsilon_0 is the electrical
permittivity of vacuum, and Z_i and Z_j are the nuclear charges of the
two atoms. The switching function S(r) is identical to that used by
<a class="reference internal" href="pair_gromacs.html"><em>pair_style lj/gromacs</em></a>. Here, the inner and outer
cutoff are the same for all pairs of atom types.</p>
<p>The following coefficients must be defined for each pair of atom types
via the <a class="reference internal" href="pair_coeff.html"><em>pair_coeff</em></a> command as in the examples above,
or in the LAMMPS data file.</p>
<ul class="simple">
<li>Z_i (atomic number for first atom type, e.g. 13.0 for aluminum)</li>
<li>Z_j (ditto for second atom type)</li>
</ul>
<p>The values of Z_i and Z_j are normally equal to the atomic
numbers of the two atom types. Thus, the user may optionally
specify only the coefficients for each I==I pair, and rely
on the obvious mixing rule for cross interactions (see below).
Note that when I==I it is required that Z_i == Z_j. When used
with <a class="reference internal" href="pair_hybrid.html"><em>hybrid/overlay</em></a> and pairs are assigned
to more than one sub-style, the mixing rule is not used and
each pair of types interacting with the ZBL sub-style must
be included in a pair_coeff command.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The numerical values of the exponential decay constants in the
screening function depend on the unit of distance. In the above
equation they are given for units of angstroms. LAMMPS will
automatically convert these values to the distance unit of the
specified LAMMPS <a class="reference internal" href="units.html"><em>units</em></a> setting. The values of Z should
always be given as multiples of a proton&#8217;s charge, e.g. 29.0 for
copper.</p>
</div>
<hr class="docutils" />
<p>Styles with a <em>cuda</em>, <em>gpu</em>, <em>intel</em>, <em>kk</em>, <em>omp</em>, or <em>opt</em> suffix are
functionally the same as the corresponding style without the suffix.
They have been optimized to run faster, depending on your available
hardware, as discussed in <a class="reference internal" href="Section_accelerate.html"><em>Section_accelerate</em></a>
of the manual. The accelerated styles take the same arguments and
should produce the same results, except for round-off and precision
issues.</p>
<p>These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
KOKKOS, USER-OMP and OPT packages, respectively. They are only
enabled if LAMMPS was built with those packages. See the <a class="reference internal" href="Section_start.html#start-3"><span>Making LAMMPS</span></a> section for more info.</p>
<p>You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the <a class="reference internal" href="Section_start.html#start-7"><span>-suffix command-line switch</span></a> when you invoke LAMMPS, or you can
use the <a class="reference internal" href="suffix.html"><em>suffix</em></a> command in your input script.</p>
<p>See <a class="reference internal" href="Section_accelerate.html"><em>Section_accelerate</em></a> of the manual for
more instructions on how to use the accelerated styles effectively.</p>
<hr class="docutils" />
<p><strong>Mixing, shift, table, tail correction, restart, rRESPA info</strong>:</p>
<p>For atom type pairs I,J and I != J, the Z_i and Z_j coefficients
can be mixed by taking Z_i and Z_j from the values specified for
I == I and J == J cases. When used
with <a class="reference internal" href="pair_hybrid.html"><em>hybrid/overlay</em></a> and pairs are assigned
to more than one sub-style, the mixing rule is not used and
each pair of types interacting with the ZBL sub-style
must be included in a pair_coeff command.
The <a class="reference internal" href="pair_modify.html"><em>pair_modify</em></a> mix option has no effect on
the mixing behavior</p>
<p>The ZBL pair style does not support the <a class="reference internal" href="pair_modify.html"><em>pair_modify</em></a>
shift option, since the ZBL interaction is already smoothed to 0.0 at
the cutoff.</p>
<p>The <a class="reference internal" href="pair_modify.html"><em>pair_modify</em></a> table option is not relevant for
this pair style.</p>
<p>This pair style does not support the <a class="reference internal" href="pair_modify.html"><em>pair_modify</em></a>
tail option for adding long-range tail corrections to energy and
pressure, since there are no corrections for a potential that goes to
0.0 at the cutoff.</p>
<p>This pair style does not write information to <a class="reference internal" href="restart.html"><em>binary restart files</em></a>, so pair_style and pair_coeff commands must be
specified in an input script that reads a restart file.</p>
<p>This pair style can only be used via the <em>pair</em> keyword of the
<a class="reference internal" href="run_style.html"><em>run_style respa</em></a> command. It does not support the
<em>inner</em>, <em>middle</em>, <em>outer</em> keywords.</p>
</div>
<hr class="docutils" />
<div class="section" id="restrictions">
<h2>Restrictions<a class="headerlink" href="#restrictions" title="Permalink to this headline">¶</a></h2>
<blockquote>
<div>none</div></blockquote>
</div>
<div class="section" id="related-commands">
<h2>Related commands<a class="headerlink" href="#related-commands" title="Permalink to this headline">¶</a></h2>
<p><a class="reference internal" href="pair_coeff.html"><em>pair_coeff</em></a></p>
<p><strong>Default:</strong> none</p>
<hr class="docutils" />
<p id="ziegler"><strong>(Ziegler)</strong> J.F. Ziegler, J. P. Biersack and U. Littmark, &#8220;The
Stopping and Range of Ions in Matter,&#8221; Volume 1, Pergamon, 1985.</p>
</div>
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