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<div class="section" id="pair-style-coul-diel-command">
<span id="index-0"></span><h1>pair_style coul/diel command</h1>
</div>
<div class="section" id="pair-style-coul-diel-omp-command">
<h1>pair_style coul/diel/omp command</h1>
<div class="section" id="syntax">
<h2>Syntax</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">pair_style</span> <span class="n">coul</span><span class="o">/</span><span class="n">diel</span> <span class="n">cutoff</span>
</pre></div>
</div>
<p>cutoff = global cutoff (distance units)</p>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">pair_style</span> <span class="n">coul</span><span class="o">/</span><span class="n">diel</span> <span class="mf">3.5</span>
<span class="n">pair_coeff</span> <span class="mi">1</span> <span class="mi">4</span> <span class="mf">78.</span> <span class="mf">1.375</span> <span class="mf">0.112</span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>Style <em>coul/diel</em> computes a Coulomb correction for implict solvent
ion interactions in which the dielectric perimittivity is distance dependent.
The dielectric permittivity epsilon_D(r) connects to limiting regimes:
One limit is defined by a small dielectric permittivity (close to vacuum)
at or close to contact seperation between the ions. At larger separations
the dielectric permittivity reaches a bulk value used in the regular Coulomb
interaction coul/long or coul/cut.
The transition is modeled by a hyperbolic function which is incorporated
in the Coulomb correction term for small ion separations as follows</p>
<img alt="_images/pair_coul_diel.jpg" class="align-center" src="_images/pair_coul_diel.jpg" />
<p>where r_me is the inflection point of epsilon_D(r) and sigma_e is a slope
defining length scale. C is the same Coulomb conversion factor as in the
pair_styles coul/cut, coul/long, and coul/debye. In this way the Coulomb
interaction between ions is corrected at small distances r. The lower
limit of epsilon_D(r-&gt;0)=5.2 due to dielectric saturation <a class="reference internal" href="#stiles"><span class="std std-ref">(Stiles)</span></a>
while the Coulomb interaction reaches its bulk limit by setting
epsilon_D(r-&gt;infty)=epsilon, the bulk value of the solvent which is 78
for water at 298K.</p>
<p>Examples of the use of this type of Coulomb interaction include implicit
solvent simulations of salt ions
<a class="reference internal" href="pair_gauss.html#lenart"><span class="std std-ref">(Lenart)</span></a> and of ionic surfactants <a class="reference internal" href="pair_gauss.html#jusufi"><span class="std std-ref">(Jusufi)</span></a>.
Note that this potential is only reasonable for implicit solvent simulations
and in combiantion with coul/cut or coul/long. It is also usually combined
with gauss/cut, see <a class="reference internal" href="pair_gauss.html#lenart"><span class="std std-ref">(Lenart)</span></a> or <a class="reference internal" href="pair_gauss.html#jusufi"><span class="std std-ref">(Jusufi)</span></a>.</p>
<p>The following coefficients must be defined for each pair of atom
types via the <a class="reference internal" href="pair_coeff.html"><span class="doc">pair_coeff</span></a> command as in the example
above, or in the data file or restart files read by the
<a class="reference internal" href="read_data.html"><span class="doc">read_data</span></a> or <a class="reference internal" href="read_restart.html"><span class="doc">read_restart</span></a>
commands:</p>
<ul class="simple">
<li>epsilon (no units)</li>
<li>r_me (distance units)</li>
<li>sigma_e (distance units)</li>
</ul>
<p>The global cutoff (r_c) specified in the pair_style command is used.</p>
<hr class="docutils" />
<p><strong>Mixing, shift, table, tail correction, restart, rRESPA info</strong>:</p>
<p>This pair style does not support parameter mixing. Coefficients must be given explicitly for each type of particle pairs.</p>
<p>This pair style supports the <a class="reference internal" href="pair_modify.html"><span class="doc">pair_modify</span></a> shift
option for the energy of the Gauss-potential portion of the pair
interaction.</p>
<p>The <a class="reference internal" href="pair_modify.html"><span class="doc">pair_modify</span></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"><span class="doc">pair_modify</span></a>
tail option for adding long-range tail corrections to energy and
pressure.</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"><span class="doc">run_style respa</span></a> command. It does not support the
<em>inner</em>, <em>middle</em>, <em>outer</em> keywords.</p>
</div>
<div class="section" id="restrictions">
<h2>Restrictions</h2>
<p>This style is part of the &#8220;user-misc&#8221; package. It is only enabled
if LAMMPS was built with that package. See the <a class="reference internal" href="Section_start.html#start-2-3"><span class="std std-ref">Making LAMMPS</span></a> section for more info.</p>
</div>
<div class="section" id="related-commands">
<h2>Related commands</h2>
<p><a class="reference internal" href="pair_coeff.html"><span class="doc">pair_coeff</span></a>
<a class="reference internal" href="pair_gauss.html"><span class="doc">pair_style gauss/cut</span></a></p>
<p><strong>Default:</strong> none</p>
<hr class="docutils" />
<p id="stiles"><strong>(Stiles)</strong> Stiles , Hubbard, and Kayser, J Chem Phys, 77,
6189 (1982).</p>
<p id="lenart"><strong>(Lenart)</strong> Lenart , Jusufi, and Panagiotopoulos, J Chem Phys, 126,
044509 (2007).</p>
<p id="jusufi"><strong>(Jusufi)</strong> Jusufi, Hynninen, and Panagiotopoulos, J Phys Chem B, 112,
13783 (2008).</p>
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