<p>where the <em>epsilon</em> parameter determines the depth of the potential
minimum located at <em>Rm</em>, and <em>alpha</em> determines the softness of the repulsion.</p>
<p>The coefficients must be defined for each species in a given particle
type via the <aclass="reference internal"href="pair_coeff.html"><spanclass="doc">pair_coeff</span></a> command as in the examples
above, where the first argument is the filename that includes the
exponential-6 parameters for each species. The file includes the
species tag followed by the <em>alpha</em>, <em>epsilon</em> and <em>Rm</em>
parameters. The format of the file is described below.</p>
<p>The second and third arguments specify the site-site interaction
potential between two species contained within two different
particles. The species tags must either correspond to the species
defined in the reaction kinetics files specified with the <aclass="reference internal"href="fix_rx.html"><spanclass="doc">fix rx</span></a> command or they must correspond to the tag “1fluid”,
signifying interaction with a product species mixture determined
through a one-fluid approximation. The interaction potential is
weighted by the geometric average of the concentrations of the two
species. The coarse-grained potential is stored before and after the
reaction kinetics solver is applied, where the difference is defined
to be the internal chemical energy (uChem).</p>
<p>The fourth and fifth arguments specify the <em>Rm</em> and <em>epsilon</em> scaling exponents.</p>
<p>The final argument specifies the interaction cutoff.</p>
<hrclass="docutils"/>
<p>The format of a tabulated file is as follows (without the
parenthesized comments):</p>
<divclass="highlight-default"><divclass="highlight"><pre><span></span><spanclass="c1"># exponential-6 parameters for various species (one or more comment or blank lines)</span>
<p>This pair style does not support mixing. Thus, coefficients for all
I,J pairs must be specified explicitly.</p>
<p>This style does not support the <aclass="reference internal"href="pair_modify.html"><spanclass="doc">pair_modify</span></a> shift option
for the energy of the exp() and 1/r^6 portion of the pair interaction.</p>
<p>This style does not support the pair_modify tail option for adding long-range
tail corrections to energy and pressure for the A,C terms in the
pair interaction.</p>
</div>
<divclass="section"id="restrictions">
<h2>Restrictions</h2>
<p>This command is part of the USER-DPD package. It is only enabled if
LAMMPS was built with that package. See the <aclass="reference internal"href="Section_start.html#start-3"><spanclass="std std-ref">Making LAMMPS</span></a> section for more info.</p>
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