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			<div class="section" id="pair-style-tersoff-zbl-command">
			<span id="index-0"></span><h1>pair_style tersoff/zbl command</h1>
			</div>
			<div class="section" id="pair-style-tersoff-zbl-gpu-command">
			<h1>pair_style tersoff/zbl/gpu command</h1>
			</div>
			<div class="section" id="pair-style-tersoff-zbl-kk-command">
			<h1>pair_style tersoff/zbl/kk command</h1>
			</div>
			<div class="section" id="pair-style-tersoff-zbl-omp-command">
			<h1>pair_style tersoff/zbl/omp command</h1>
			<div class="section" id="syntax">
			<h2>Syntax</h2>
			<pre class="literal-block">
			pair_style tersoff/zbl
			</pre>
			</div>
			<div class="section" id="examples">
			<h2>Examples</h2>
			<pre class="literal-block">
			pair_style tersoff/zbl
			pair_coeff * * SiC.tersoff.zbl Si C Si
			</pre>
			</div>
			<div class="section" id="description">
			<h2>Description</h2>
			<p>The <em>tersoff/zbl</em> style computes a 3-body Tersoff potential
			<a class="reference internal" href="#tersoff-1"><span class="std std-ref">(Tersoff_1)</span></a> with a close-separation pairwise modification
			based on a Coulomb potential and the Ziegler-Biersack-Littmark
			universal screening function <a class="reference internal" href="#zbl"><span class="std std-ref">(ZBL)</span></a>, giving the energy E of a
			system of atoms as</p>
			<img alt="_images/pair_tersoff_zbl.jpg" class="align-center" src="_images/pair_tersoff_zbl.jpg" />
			<p>The f_F term is a fermi-like function used to smoothly connect the ZBL
			repulsive potential with the Tersoff potential. There are 2
			parameters used to adjust it: A_F and r_C. A_F controls how “sharp”
			the transition is between the two, and r_C is essentially the cutoff
			for the ZBL potential.</p>
			<p>For the ZBL portion, there are two terms. The first is the Coulomb
			repulsive term, with Z1, Z2 as the number of protons in each nucleus,
			e as the electron charge (1 for metal and real units) and epsilon0 as
			the permittivity of vacuum. The second part is the ZBL universal
			screening function, with a0 being the Bohr radius (typically 0.529
			Angstroms), and the remainder of the coefficients provided by the
			original paper. This screening function should be applicable to most
			systems. However, it is only accurate for small separations
			(i.e. less than 1 Angstrom).</p>
			<p>For the Tersoff portion, f_R is a two-body term and f_A includes
			three-body interactions. The summations in the formula are over all
			neighbors J and K of atom I within a cutoff distance = R + D.</p>
			<p>Only a single pair_coeff command is used with the <em>tersoff/zbl</em> style
			which specifies a Tersoff/ZBL 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 Tersoff/ZBL elements to atom types</li>
			</ul>
			<p>See the <a class="reference internal" href="pair_coeff.html"><span class="doc">pair_coeff</span></a> doc page for alternate ways
			to specify the path for the potential file.</p>
			<p>As an example, imagine the SiC.tersoff.zbl file has Tersoff/ZBL values
			for Si and C. If your LAMMPS simulation has 4 atoms types and you
			want the 1st 3 to be Si, and the 4th to be C, you would use the
			following pair_coeff command:</p>
			<pre class="literal-block">
			pair_coeff * * SiC.tersoff Si Si Si C
			</pre>
			<p>The 1st 2 arguments must be * * so as to span all LAMMPS atom types.
			The first three Si arguments map LAMMPS atom types 1,2,3 to the Si
			element in the Tersoff/ZBL file. The final C argument maps LAMMPS
			atom type 4 to the C element in the Tersoff/ZBL file. If a mapping
			value is specified as NULL, the mapping is not performed. This can be
			used when a <em>tersoff/zbl</em> potential is used as part of the <em>hybrid</em>
			pair style. The NULL values are placeholders for atom types that will
			be used with other potentials.</p>
			<p>Tersoff/ZBL files in the <em>potentials</em> directory of the LAMMPS
			distribution have a ”.tersoff.zbl” suffix. Lines that are not blank
			or comments (starting with #) define parameters for a triplet of
			elements. The parameters in a single entry correspond to coefficients
			in the formula above:</p>
			<ul class="simple">
			<li>element 1 (the center atom in a 3-body interaction)</li>
			<li>element 2 (the atom bonded to the center atom)</li>
			<li>element 3 (the atom influencing the 1-2 bond in a bond-order sense)</li>
			<li>m</li>
			<li>gamma</li>
			<li>lambda3 (1/distance units)</li>
			<li>c</li>
			<li>d</li>
			<li>costheta0 (can be a value < -1 or > 1)</li>
			<li>n</li>
			<li>beta</li>
			<li>lambda2 (1/distance units)</li>
			<li>B (energy units)</li>
			<li>R (distance units)</li>
			<li>D (distance units)</li>
			<li>lambda1 (1/distance units)</li>
			<li>A (energy units)</li>
			<li>Z_i</li>
			<li>Z_j</li>
			<li>ZBLcut (distance units)</li>
			<li>ZBLexpscale (1/distance units)</li>
			</ul>
			<p>The n, beta, lambda2, B, lambda1, and A parameters are only used for
			two-body interactions. The m, gamma, lambda3, c, d, and costheta0
			parameters are only used for three-body interactions. The R and D
			parameters are used for both two-body and three-body interactions. The
			Z_i,Z_j, ZBLcut, ZBLexpscale parameters are used in the ZBL repulsive
			portion of the potential and in the Fermi-like function. The
			non-annotated parameters are unitless. The value of m must be 3 or 1.</p>
			<p>The Tersoff/ZBL potential file must contain entries for all the
			elements listed in the pair_coeff command. It can also contain
			entries for additional elements not being used in a particular
			simulation; LAMMPS ignores those entries.</p>
			<p>For a single-element simulation, only a single entry is required
			(e.g. SiSiSi). For a two-element simulation, the file must contain 8
			entries (for SiSiSi, SiSiC, SiCSi, SiCC, CSiSi, CSiC, CCSi, CCC), that
			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="#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 portion of the 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="#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 potential <a class="reference internal" href="#tersoff-2"><span class="std std-ref">(Tersoff_2)</span></a>.</p>
			<p>LAMMPS parameter values for Tersoff_2 can be obtained as follows:
			gamma = omega_ijk, lambda3 = 0 and the value of
			m has no effect. The parameters for species i and j can be calculated
			using the Tersoff_2 mixing rules:</p>
			<img alt="_images/pair_tersoff_2.jpg" class="align-center" src="_images/pair_tersoff_2.jpg" />
			<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. Also thanks to Ram Devanathan for
			providing the base ZBL implementation.</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_accelerate</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_accelerate</span></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, 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
			<em>inner</em>, <em>middle</em>, <em>outer</em> keywords.</p>
			</div>
			<hr class="docutils" />
			<div class="section" id="restrictions">
			<h2>Restrictions</h2>
			<p>This pair style is part of the MANYBODY package. It is only enabled
			if LAMMPS was built with that package (which it is by default). 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>This pair style requires the <a class="reference internal" href="newton.html"><span class="doc">newton</span></a> setting to be “on”
			for pair interactions.</p>
			<p>The Tersoff/ZBL potential files provided with LAMMPS (see the
			potentials directory) are parameterized for metal <a class="reference internal" href="units.html"><span class="doc">units</span></a>.
			You can use the Tersoff potential with any LAMMPS units, but you would
			need to create your own Tersoff potential file with coefficients
			listed in the appropriate units if your simulation doesn’t use “metal”
			units.</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></p>
			<p><strong>Default:</strong> none</p>
			<hr class="docutils" />
			<p id="tersoff-1"><strong>(Tersoff_1)</strong> J. Tersoff, Phys Rev B, 37, 6991 (1988).</p>
			<p id="zbl"><strong>(ZBL)</strong> J.F. Ziegler, J.P. Biersack, U. Littmark, ‘Stopping and Ranges
			of Ions in Matter’ Vol 1, 1985, Pergamon Press.</p>
			<p id="albe"><strong>(Albe)</strong> J. Nord, K. Albe, P. Erhart and K. Nordlund, J. Phys.:
			Condens. Matter, 15, 5649(2003).</p>
			<p id="tersoff-2"><strong>(Tersoff_2)</strong> J. Tersoff, Phys Rev B, 39, 5566 (1989); errata (PRB 41, 3248)</p>
			</div>
			</div>


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