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<div class="section" id="frequency">
<span id="sec-freq"></span><h1>Frequency<a class="headerlink" href="#frequency" title="Permalink to this headline">¶</a></h1>
<dl class="function">
<dt id="driver.frequency">
<tt class="descname">frequency</tt><big>(</big><em>name</em><span class="optional">[</span>, <em>func</em>, <em>mode</em>, <em>dertype</em>, <em>irrep</em>, <em>molecule</em><span class="optional">]</span><big>)</big><a class="reference internal" href="_modules/driver.html#frequency"><span class="viewcode-link">[source]</span></a><a class="headerlink" href="#driver.frequency" title="Permalink to this definition">¶</a></dt>
<dd><p>Function to compute harmonic vibrational frequencies.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Aliases :</th><td class="field-body">frequencies(), freq()</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body">(<em>float</em>) Total electronic energy in Hartrees.</td>
</tr>
</tbody>
</table>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Analytic hessians are not available. Frequencies will proceed through
finite differences according to availability of gradients or energies.</p>
</div>
<div class="admonition caution">
<p class="first admonition-title">Caution</p>
<p>Some features are not yet implemented. Buy a developer a coffee.</p>
<ul class="last simple">
<li>Implement sow/reap mode for finite difference of gradients. Presently only for findif of energies.</li>
</ul>
</div>
<table class="docutils field-list" frame="void" id="table-freq-gen" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
<li><strong>name</strong> (<em>string</em>) – <p><tt class="docutils literal"><span class="pre">'scf'</span></tt> || <tt class="docutils literal"><span class="pre">'df-mp2'</span></tt> || <tt class="docutils literal"><span class="pre">'ci5'</span></tt> || etc.</p>
<p>First argument, usually unlabeled. Indicates the computational method
to be applied to the system.</p>
</li>
<li><strong>dertype</strong> (<a class="reference internal" href="notes_py.html#op-py-dertype"><em>dertype</em></a>) – <p><img class="math" src="_images/math/843622567e12d686e4e2f94ddfcb444e8ecde0d2.png" alt="\Rightarrow" style="vertical-align: -1px"/> <tt class="docutils literal"><span class="pre">'hessian'</span></tt> <img class="math" src="_images/math/d773375e7bd7f973b121cd9403ad90d3806d6996.png" alt="\Leftarrow" style="vertical-align: -1px"/> || <tt class="docutils literal"><span class="pre">'gradient'</span></tt> || <tt class="docutils literal"><span class="pre">'energy'</span></tt></p>
<p>Indicates whether analytic (if available- they’re not), finite
difference of gradients (if available) or finite difference of
energies is to be performed.</p>
</li>
<li><strong>mode</strong> (<em>string</em>) – <p><img class="math" src="_images/math/843622567e12d686e4e2f94ddfcb444e8ecde0d2.png" alt="\Rightarrow" style="vertical-align: -1px"/> <tt class="docutils literal"><span class="pre">'continuous'</span></tt> <img class="math" src="_images/math/d773375e7bd7f973b121cd9403ad90d3806d6996.png" alt="\Leftarrow" style="vertical-align: -1px"/> || <tt class="docutils literal"><span class="pre">'sow'</span></tt> || <tt class="docutils literal"><span class="pre">'reap'</span></tt></p>
<p>For a finite difference of energies or gradients frequency, indicates
whether the calculations required to complet the frequency are to be run
in one file (<tt class="docutils literal"><span class="pre">'continuous'</span></tt>) or are to be farmed out in an
embarrassingly parallel fashion (<tt class="docutils literal"><span class="pre">'sow'</span></tt>/<tt class="docutils literal"><span class="pre">'reap'</span></tt>)/ For the latter,
run an initial job with <tt class="docutils literal"><span class="pre">'sow'</span></tt> and follow instructions in its output file.</p>
</li>
<li><strong>irrep</strong> (<em>int or string</em>) – <p><img class="math" src="_images/math/843622567e12d686e4e2f94ddfcb444e8ecde0d2.png" alt="\Rightarrow" style="vertical-align: -1px"/> <tt class="docutils literal"><span class="pre">-1</span></tt> <img class="math" src="_images/math/d773375e7bd7f973b121cd9403ad90d3806d6996.png" alt="\Leftarrow" style="vertical-align: -1px"/> || <tt class="docutils literal"><span class="pre">1</span></tt> || <tt class="docutils literal"><span class="pre">'b2'</span></tt> || <tt class="docutils literal"><span class="pre">'App'</span></tt> || etc.</p>
<p>Indicates which symmetry block (<a class="reference internal" href="psithonmol.html#table-irrepordering"><em>Cotton</em></a> ordering) of vibrational
frequencies to be computed. <tt class="docutils literal"><span class="pre">1</span></tt>, <tt class="docutils literal"><span class="pre">'1'</span></tt>, or <tt class="docutils literal"><span class="pre">'a1'</span></tt> represents
<img class="math" src="_images/math/1ab39d761413804680d26d972381f028001562f5.png" alt="a_1" style="vertical-align: -4px"/>, requesting only the totally symmetric modes.
<tt class="docutils literal"><span class="pre">-1</span></tt> indicates a full frequency calculation.</p>
</li>
<li><strong>molecule</strong> (<a class="reference internal" href="notes_py.html#op-py-molecule"><em>molecule</em></a>) – <p><tt class="docutils literal"><span class="pre">h2o</span></tt> || etc.</p>
<p>The target molecule, if not the last molecule defined.</p>
</li>
</ul>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Examples :</th><td class="field-body"></td>
</tr>
</tbody>
</table>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="c"># [1] <example description></span>
<span class="gp">>>> </span><span class="o"><</span><span class="n">example</span> <span class="n">python</span> <span class="n">command</span><span class="o">></span>
</pre></div>
</div>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="c"># [2] Frequency calculation for b2 modes through finite difference of gradients</span>
<span class="gp">>>> </span><span class="n">frequencies</span><span class="p">(</span><span class="s">'scf'</span><span class="p">,</span> <span class="n">dertype</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span> <span class="n">irrep</span><span class="o">=</span><span class="mi">4</span><span class="p">)</span>
</pre></div>
</div>
</dd></dl>
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