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<div class="section" id="pair-style-gauss-command">
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<span id="index-0"></span><h1>pair_style gauss command</h1>
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</div>
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<div class="section" id="pair-style-gauss-gpu-command">
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<h1>pair_style gauss/gpu command</h1>
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</div>
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<div class="section" id="pair-style-gauss-omp-command">
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<h1>pair_style gauss/omp command</h1>
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</div>
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<div class="section" id="pair-style-gauss-cut-command">
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<h1>pair_style gauss/cut command</h1>
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</div>
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<div class="section" id="pair-style-gauss-cut-omp-command">
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<h1>pair_style gauss/cut/omp command</h1>
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<div class="section" id="syntax">
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<h2>Syntax</h2>
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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">pair_style</span> <span class="n">gauss</span> <span class="n">cutoff</span>
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<span class="n">pair_style</span> <span class="n">gauss</span><span class="o">/</span><span class="n">cut</span> <span class="n">cutoff</span>
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</pre></div>
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</div>
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<ul class="simple">
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<li>cutoff = global cutoff for Gauss interactions (distance units)</li>
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</ul>
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</div>
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<div class="section" id="examples">
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<h2>Examples</h2>
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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">pair_style</span> <span class="n">gauss</span> <span class="mf">12.0</span>
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<span class="n">pair_coeff</span> <span class="o">*</span> <span class="o">*</span> <span class="mf">1.0</span> <span class="mf">0.9</span>
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<span class="n">pair_coeff</span> <span class="mi">1</span> <span class="mi">4</span> <span class="mf">1.0</span> <span class="mf">0.9</span> <span class="mf">10.0</span>
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</pre></div>
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</div>
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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">pair_style</span> <span class="n">gauss</span><span class="o">/</span><span class="n">cut</span> <span class="mf">3.5</span>
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<span class="n">pair_coeff</span> <span class="mi">1</span> <span class="mi">4</span> <span class="mf">0.2805</span> <span class="mf">1.45</span> <span class="mf">0.112</span>
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</pre></div>
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</div>
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</div>
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<div class="section" id="description">
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<h2>Description</h2>
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<p>Style <em>gauss</em> computes a tethering potential of the form</p>
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<img alt="_images/pair_gauss.jpg" class="align-center" src="_images/pair_gauss.jpg" />
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<p>between an atom and its corresponding tether site which will typically
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be a frozen atom in the simulation. Rc is the cutoff.</p>
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<p>The following coefficients must be defined for each pair of atom types
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via the <a class="reference internal" href="pair_coeff.html"><span class="doc">pair_coeff</span></a> command as in the examples above,
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or in the data file or restart files read by the
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<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>
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commands:</p>
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<ul class="simple">
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<li>A (energy units)</li>
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<li>B (1/distance^2 units)</li>
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<li>cutoff (distance units)</li>
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</ul>
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<p>The last coefficient is optional. If not specified, the global cutoff
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is used.</p>
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<p>Style <em>gauss/cut</em> computes a generalized Gaussian interaction potential
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between pairs of particles:</p>
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<img alt="_images/pair_gauss_cut.jpg" class="align-center" src="_images/pair_gauss_cut.jpg" />
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<p>where H determines together with the standard deviation sigma_h the
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peak height of the Gaussian function, and r_mh the peak position.
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Examples of the use of the Gaussian potentials include implicit
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solvent simulations of salt ions <a class="reference internal" href="#lenart"><span class="std std-ref">(Lenart)</span></a> and of surfactants
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<a class="reference internal" href="#jusufi"><span class="std std-ref">(Jusufi)</span></a>. In these instances the Gaussian potential mimics
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the hydration barrier between a pair of particles. The hydration
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barrier is located at r_mh and has a width of sigma_h. The prefactor
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determines the hight of the potential barrier.</p>
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<p>The following coefficients must be defined for each pair of atom types
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via the <a class="reference internal" href="pair_coeff.html"><span class="doc">pair_coeff</span></a> command as in the example above,
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or in the data file or restart files read by the
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<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>
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commands:</p>
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<ul class="simple">
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<li>H (energy * distance units)</li>
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<li>r_mh (distance units)</li>
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<li>sigma_h (distance units)</li>
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</ul>
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<p>The global cutoff (r_c) specified in the pair_style command is used.</p>
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<hr class="docutils" />
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<p>Styles with a <em>cuda</em>, <em>gpu</em>, <em>intel</em>, <em>kk</em>, <em>omp</em>, or <em>opt</em> suffix are
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed in <a class="reference internal" href="Section_accelerate.html"><span class="doc">Section_accelerate</span></a>
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of the manual. The accelerated styles take the same arguments and
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should produce the same results, except for round-off and precision
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issues.</p>
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<p>These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
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KOKKOS, USER-OMP and OPT packages, respectively. They are only
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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>
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<p>You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the “-suffix command-line
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switch7_Section_start.html#start_6 when you invoke LAMMPS, or you can
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use the <a class="reference internal" href="suffix.html"><span class="doc">suffix</span></a> command in your input script.</p>
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<p>See <a class="reference internal" href="Section_accelerate.html"><span class="doc">Section_accelerate</span></a> of the manual for
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more instructions on how to use the accelerated styles effectively.</p>
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<hr class="docutils" />
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<p><strong>Mixing, shift, table, tail correction, restart, rRESPA info</strong>:</p>
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<p>These pair styles do not support mixing. Thus, coefficients for all
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I,J pairs must be specified explicitly.</p>
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<p>The <em>gauss</em> style does not support the <a class="reference internal" href="pair_modify.html"><span class="doc">pair_modify</span></a>
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shift option. There is no effect due to the Gaussian well beyond the
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cutoff; hence reasonable cutoffs need to be specified.</p>
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<p>The <em>gauss/cut</em> style supports the <a class="reference internal" href="pair_modify.html"><span class="doc">pair_modify</span></a> shift
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option for the energy of the Gauss-potential portion of the pair
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interaction.</p>
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<p>The <a class="reference internal" href="pair_modify.html"><span class="doc">pair_modify</span></a> table and tail options are not
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relevant for these pair styles.</p>
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<p>These pair styles write their information to <a class="reference internal" href="restart.html"><span class="doc">binary restart files</span></a>, so pair_style and pair_coeff commands do not need
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to be specified in an input script that reads a restart file.</p>
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<p>These pair styles can only be used via the <em>pair</em> keyword of the
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<a class="reference internal" href="run_style.html"><span class="doc">run_style respa</span></a> command. They do not support the
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<em>inner</em>, <em>middle</em>, <em>outer</em> keywords.</p>
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<p>The <em>gauss</em> pair style tallies an “occupancy” count of how many Gaussian-well
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sites have an atom within the distance at which the force is a maximum
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= sqrt(0.5/b). This quantity can be accessed via the <a class="reference internal" href="compute_pair.html"><span class="doc">compute pair</span></a> command as a vector of values of length 1.</p>
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<p>To print this quantity to the log file (with a descriptive column
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heading) the following commands could be included in an input script:</p>
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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">compute</span> <span class="n">gauss</span> <span class="nb">all</span> <span class="n">pair</span> <span class="n">gauss</span>
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<span class="n">variable</span> <span class="n">occ</span> <span class="n">equal</span> <span class="n">c_gauss</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span>
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<span class="n">thermo_style</span> <span class="n">custom</span> <span class="n">step</span> <span class="n">temp</span> <span class="n">epair</span> <span class="n">v_occ</span>
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</pre></div>
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</div>
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</div>
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<hr class="docutils" />
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<div class="section" id="restrictions">
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<h2>Restrictions</h2>
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<p>The <em>gauss/cut</em> style is part of the “user-misc” package. It is only
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enabled if LAMMPS is build with that package. See the <span class="xref std std-ref">Making of LAMMPS</span> section for more info.</p>
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</div>
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<div class="section" id="related-commands">
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<h2>Related commands</h2>
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<p><a class="reference internal" href="pair_coeff.html"><span class="doc">pair_coeff</span></a>,
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<a class="reference internal" href="pair_coul_diel.html"><span class="doc">pair_style coul/diel</span></a></p>
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<p><strong>Default:</strong> none</p>
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<p id="lenart"><strong>(Lenart)</strong> Lenart , Jusufi, and Panagiotopoulos, J Chem Phys, 126,
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044509 (2007).</p>
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<p id="jusufi"><strong>(Jusufi)</strong> Jusufi, Hynninen, and Panagiotopoulos, J Phys Chem B, 112,
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13783 (2008).</p>
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