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<title>pair_style meam/sw/spline &mdash; LAMMPS 9 Dec 2015 documentation</title>
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<div class="section" id="pair-style-meam-sw-spline">
<h1>pair_style meam/sw/spline<a class="headerlink" href="#pair-style-meam-sw-spline" title="Permalink to this headline">¶</a></h1>
</div>
<div class="section" id="pair-style-meam-sw-spline-omp">
<h1>pair_style meam/sw/spline/omp<a class="headerlink" href="#pair-style-meam-sw-spline-omp" 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 meam/sw/spline
</pre></div>
</div>
</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 meam/sw/spline
pair_coeff * * Ti.meam.sw.spline Ti
pair_coeff * * Ti.meam.sw.spline Ti Ti Ti
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
<p>The <em>meam/sw/spline</em> style computes pairwise interactions for metals
using a variant of modified embedded-atom method (MEAM) potentials
<a class="reference internal" href="#lenosky"><span>(Lenosky)</span></a> with an additional Stillinger-Weber (SW) term
<a class="reference internal" href="pair_sw.html#stillinger"><span>(Stillinger)</span></a> in the energy. This form of the potential
was first proposed by Nicklas, Fellinger, and Park
<a class="reference internal" href="#nicklas"><span>(Nicklas)</span></a>. We refer to it as MEAM+SW. The total energy E
is given by</p>
<img alt="_images/pair_meam_sw_spline.jpg" class="align-center" src="_images/pair_meam_sw_spline.jpg" />
<p>where rho_I is the density at atom I, theta_JIK is the angle between
atoms J, I, and K centered on atom I. The seven functions
Phi, F, G, U, rho, f, and g are represented by cubic splines.</p>
<p>The cutoffs and the coefficients for these spline functions are listed
in a parameter file which is specified by the
<a class="reference internal" href="pair_coeff.html"><em>pair_coeff</em></a> command. Parameter files for different
elements are included in the &#8220;potentials&#8221; directory of the LAMMPS
distribution and have a &#8221;.meam.sw.spline&#8221; file suffix. All of these
files are parameterized in terms of LAMMPS <a class="reference internal" href="units.html"><em>metal units</em></a>.</p>
<p>Note that unlike for other potentials, cutoffs for spline-based
MEAM+SW potentials are not set in the pair_style or pair_coeff
command; they are specified in the potential files themselves.</p>
<p>Unlike the EAM pair style, which retrieves the atomic mass from the
potential file, the spline-based MEAM+SW potentials do not include
mass information; thus you need to use the <a class="reference internal" href="mass.html"><em>mass</em></a> command to
specify it.</p>
<p>Only a single pair_coeff command is used with the meam/sw/spline style
which specifies a potential file with parameters for all needed
elements. These are mapped to LAMMPS atom types by specifying N
additional arguments after the filename in the pair_coeff command,
where N is the number of LAMMPS atom types:</p>
<ul class="simple">
<li>filename</li>
<li>N element names = mapping of spline-based MEAM+SW elements to atom types</li>
</ul>
<p>See the <a class="reference internal" href="pair_coeff.html"><em>pair_coeff</em></a> doc page for alternate ways
to specify the path for the potential file.</p>
<p>As an example, imagine the Ti.meam.sw.spline file has values for Ti.
If your LAMMPS simulation has 3 atoms types and they are all to be
treated with this potential, you would use the following pair_coeff
command:</p>
<p>pair_coeff * * Ti.meam.sw.spline Ti Ti Ti</p>
<p>The 1st 2 arguments must be * * so as to span all LAMMPS atom types.
The three Ti arguments map LAMMPS atom types 1,2,3 to the Ti element
in the potential file. If a mapping value is specified as NULL, the
mapping is not performed. This can be used when a <em>meam/sw/spline</em>
potential is used as part of the hybrid pair style. The NULL values
are placeholders for atom types that will be used with other
potentials.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The <em>meam/sw/spline</em> style currently supports only
single-element MEAM+SW potentials. It may be extended for alloy
systems in the future.</p>
</div>
<p>Example input scripts that use this pair style are provided
in the examples/USER/misc/meam_sw_spline directory.</p>
<hr class="docutils" />
<p><strong>Mixing, shift, table, tail correction, restart, rRESPA info</strong>:</p>
<p>The pair style does not support multiple element types or mixing.
It has been designed for pure elements only.</p>
<p>This pair style does not support the <a class="reference internal" href="pair_modify.html"><em>pair_modify</em></a>
shift, table, and tail options.</p>
<p>The <em>meam/sw/spline</em> pair style does not write its information to
<a class="reference internal" href="restart.html"><em>binary restart files</em></a>, since it is stored in an external
potential parameter file. Thus, you need to re-specify the pair_style
and pair_coeff commands in an input script that reads a restart file.</p>
<p>The <em>meam/sw/spline</em> 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. They do 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>
<p>This pair style requires the <a class="reference internal" href="newton.html"><em>newton</em></a> setting to be &#8220;on&#8221;
for pair interactions.</p>
<p>This pair style is only enabled if LAMMPS was built with the USER-MISC package.
See the <a class="reference internal" href="Section_start.html#start-3"><span>Making LAMMPS</span></a> section for more info.</p>
</div>
<div class="section" id="related-commands">
<h2>Related commands<a class="headerlink" href="#related-commands" title="Permalink to this headline">¶</a></h2>
<p><a class="reference internal" href="pair_coeff.html"><em>pair_coeff</em></a>, <a class="reference internal" href="pair_meam.html"><em>pair_style meam</em></a>,
<a class="reference internal" href="pair_meam_spline.html"><em>pair_style meam/spline</em></a></p>
<p><strong>Default:</strong> none</p>
<hr class="docutils" />
<p id="lenosky"><strong>(Lenosky)</strong> Lenosky, Sadigh, Alonso, Bulatov, de la Rubia, Kim, Voter,
Kress, Modell. Simul. Mater. Sci. Eng. 8, 825 (2000).</p>
<p id="stillinger"><strong>(Stillinger)</strong> Stillinger, Weber, Phys. Rev. B 31, 5262 (1985).</p>
<p id="nicklas"><strong>(Nicklas)</strong>
The spline-based MEAM+SW format was first devised and used to develop
potentials for bcc transition metals by Jeremy Nicklas, Michael Fellinger,
and Hyoungki Park at The Ohio State University.</p>
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