<p>style = <em>tersoff</em> or <em>tersoff/table</em> or <em>tersoff/gpu</em> or <em>tersoff/omp</em> or <em>tersoff/table/omp</em></p>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<pre class="literal-block">
pair_style tersoff
pair_coeff * * Si.tersoff Si
pair_coeff * * SiC.tersoff Si C Si
</pre>
<pre class="literal-block">
pair_style tersoff/table
pair_coeff * * SiCGe.tersoff Si(D)
</pre>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>The <em>tersoff</em> style computes a 3-body Tersoff potential
<a class="reference internal" href="pair_tersoff_zbl.html#tersoff-1"><span class="std std-ref">(Tersoff_1)</span></a> for the energy E of a system of atoms as</p>
specify Tersoff parameters for all permutations of the two elements
interacting in three-body configurations. Thus for 3 elements, 27
entries would be required, etc.</p>
<p>As annotated above, the first element in the entry is the center atom
in a three-body interaction and it is bonded to the 2nd atom and the
bond is influenced by the 3rd atom. Thus an entry for SiCC means Si
bonded to a C with another C atom influencing the bond. Thus
three-body parameters for SiCSi and SiSiC entries will not, in
general, be the same. The parameters used for the two-body
interaction come from the entry where the 2nd element is repeated.
Thus the two-body parameters for Si interacting with C, comes from the
SiCC entry.</p>
<p>The parameters used for a particular
three-body interaction come from the entry with the corresponding
three elements. The parameters used only for two-body interactions
(n, beta, lambda2, B, lambda1, and A) in entries whose 2nd and 3rd
element are different (e.g. SiCSi) are not used for anything and can
be set to 0.0 if desired.</p>
<p>Note that the twobody parameters in entries such as SiCC and CSiSi
are often the same, due to the common use of symmetric mixing rules,
but this is not always the case. For example, the beta and n parameters in
Tersoff_2 <a class="reference internal" href="pair_tersoff_zbl.html#tersoff-2"><span class="std std-ref">(Tersoff_2)</span></a> are not symmetric.</p>
<p>We chose the above form so as to enable users to define all commonly
used variants of the Tersoff potential. In particular, our form
reduces to the original Tersoff form when m = 3 and gamma = 1, while
it reduces to the form of <a class="reference internal" href="pair_tersoff_zbl.html#albe"><span class="std std-ref">Albe et al.</span></a> when beta = 1 and m = 1.
Note that in the current Tersoff implementation in LAMMPS, m must be
specified as either 3 or 1. Tersoff used a slightly different but
equivalent form for alloys, which we will refer to as Tersoff_2
<p>Tersoff_2 parameters R and S must be converted to the LAMMPS
parameters R and D (R is different in both forms), using the following
relations: R=(R’+S’)/2 and D=(S’-R’)/2, where the primes indicate the
Tersoff_2 parameters.</p>
<p>In the potentials directory, the file SiCGe.tersoff provides the
LAMMPS parameters for Tersoff’s various versions of Si, as well as his
alloy parameters for Si, C, and Ge. This file can be used for pure Si,
(three different versions), pure C, pure Ge, binary SiC, and binary
SiGe. LAMMPS will generate an error if this file is used with any
combination involving C and Ge, since there are no entries for the GeC
interactions (Tersoff did not publish parameters for this
cross-interaction.) Tersoff files are also provided for the SiC alloy
(SiC.tersoff) and the GaN (GaN.tersoff) alloys.</p>
<p>Many thanks to Rutuparna Narulkar, David Farrell, and Xiaowang Zhou
for helping clarify how Tersoff parameters for alloys have been
defined in various papers.</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 in <a class="reference internal" href="Section_accelerate.html"><span class="doc">Section 5</span></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 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 class="std std-ref">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 class="std std-ref">-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 <a class="reference internal" href="Section_accelerate.html"><span class="doc">Section 5</span></a> of the manual for
more instructions on how to use the accelerated styles effectively.</p>
<p>For atom type pairs I,J and I != J, where types I and J correspond to
two different element types, mixing is performed by LAMMPS as
described above from values in the potential file.</p>
<p>This pair style does not support the <a class="reference internal" href="pair_modify.html"><span class="doc">pair_modify</span></a>
shift, table, and tail options.</p>
<p>This pair style does not write its information to <a class="reference internal" href="restart.html"><span class="doc">binary restart files</span></a>, since it is stored in potential files. Thus, you
need to re-specify the pair_style and pair_coeff commands 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"><span class="doc">run_style respa</span></a> command. It does not support the
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