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<div class="section" id="bond-coeff-command">
<span id="index-0"></span><h1>bond_coeff command<a class="headerlink" href="#bond-coeff-command" title="Permalink to this headline"></a></h1>
<div class="section" id="syntax">
<h2>Syntax<a class="headerlink" href="#syntax" title="Permalink to this headline"></a></h2>
<div class="highlight-python"><div class="highlight"><pre>bond_coeff N args
</pre></div>
</div>
<ul class="simple">
<li>N = bond type (see asterisk form below)</li>
<li>args = coefficients for one or more bond types</li>
</ul>
</div>
<div class="section" id="examples">
<h2>Examples<a class="headerlink" href="#examples" title="Permalink to this headline"></a></h2>
<div class="highlight-python"><div class="highlight"><pre>bond_coeff 5 80.0 1.2
bond_coeff * 30.0 1.5 1.0 1.0
bond_coeff 1*4 30.0 1.5 1.0 1.0
bond_coeff 1 harmonic 200.0 1.0
</pre></div>
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<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline"></a></h2>
<p>Specify the bond force field coefficients for one or more bond types.
The number and meaning of the coefficients depends on the bond style.
Bond coefficients can also be set in the data file read by the
<a class="reference internal" href="read_data.html"><em>read_data</em></a> command or in a restart file.</p>
<p>N can be specified in one of two ways. An explicit numeric value can
be used, as in the 1st example above. Or a wild-card asterisk can be
used to set the coefficients for multiple bond types. This takes the
form &#8220;*&#8221; or &#8220;<em>n&#8221; or &#8220;n</em>&#8221; or &#8220;m*n&#8221;. If N = the number of bond types,
then an asterisk with no numeric values means all types from 1 to N. A
leading asterisk means all types from 1 to n (inclusive). A trailing
asterisk means all types from n to N (inclusive). A middle asterisk
means all types from m to n (inclusive).</p>
<p>Note that using a bond_coeff command can override a previous setting
for the same bond type. For example, these commands set the coeffs
for all bond types, then overwrite the coeffs for just bond type 2:</p>
<div class="highlight-python"><div class="highlight"><pre>bond_coeff * 100.0 1.2
bond_coeff 2 200.0 1.2
</pre></div>
</div>
<p>A line in a data file that specifies bond coefficients uses the exact
same format as the arguments of the bond_coeff command in an input
script, except that wild-card asterisks should not be used since
coefficients for all N types must be listed in the file. For example,
under the &#8220;Bond Coeffs&#8221; section of a data file, the line that
corresponds to the 1st example above would be listed as</p>
<div class="highlight-python"><div class="highlight"><pre>5 80.0 1.2
</pre></div>
</div>
<hr class="docutils" />
<p>Here is an alphabetic list of bond styles defined in LAMMPS. Click on
the style to display the formula it computes and coefficients
specified by the associated <a class="reference internal" href=""><em>bond_coeff</em></a> command.</p>
<p>Note that here are also additional bond styles submitted by users
which are included in the LAMMPS distribution. The list of these with
links to the individual styles are given in the bond section of <a class="reference internal" href="Section_commands.html#cmd-5"><span>this page</span></a>.</p>
<ul class="simple">
<li><a class="reference internal" href="bond_none.html"><em>bond_style none</em></a> - turn off bonded interactions</li>
<li><a class="reference internal" href="bond_hybrid.html"><em>bond_style hybrid</em></a> - define multiple styles of bond interactions</li>
<li><a class="reference internal" href="bond_class2.html"><em>bond_style class2</em></a> - COMPASS (class 2) bond</li>
<li><a class="reference internal" href="bond_fene.html"><em>bond_style fene</em></a> - FENE (finite-extensible non-linear elastic) bond</li>
<li><a class="reference internal" href="bond_fene_expand.html"><em>bond_style fene/expand</em></a> - FENE bonds with variable size particles</li>
<li><a class="reference internal" href="bond_harmonic.html"><em>bond_style harmonic</em></a> - harmonic bond</li>
<li><a class="reference internal" href="bond_morse.html"><em>bond_style morse</em></a> - Morse bond</li>
<li><a class="reference internal" href="bond_nonlinear.html"><em>bond_style nonlinear</em></a> - nonlinear bond</li>
<li><a class="reference internal" href="bond_quartic.html"><em>bond_style quartic</em></a> - breakable quartic bond</li>
<li><a class="reference internal" href="bond_table.html"><em>bond_style table</em></a> - tabulated by bond length</li>
</ul>
</div>
<hr class="docutils" />
<div class="section" id="restrictions">
<h2>Restrictions<a class="headerlink" href="#restrictions" title="Permalink to this headline"></a></h2>
<p>This command must come after the simulation box is defined by a
<a class="reference internal" href="read_data.html"><em>read_data</em></a>, <a class="reference internal" href="read_restart.html"><em>read_restart</em></a>, or
<a class="reference internal" href="create_box.html"><em>create_box</em></a> command.</p>
<p>A bond style must be defined before any bond coefficients are set,
either in the input script or in a data file.</p>
</div>
<div class="section" id="related-commands">
<h2>Related commands<a class="headerlink" href="#related-commands" title="Permalink to this headline"></a></h2>
<p><a class="reference internal" href="bond_style.html"><em>bond_style</em></a></p>
<p><strong>Default:</strong> none</p>
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