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<li class="toctree-l1"><a class="reference internal" href="Section_intro.html">1. Introduction</a></li>
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<div class="section" id="min-style-command">
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<span id="index-0"></span><h1>min_style 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">min_style</span> <span class="n">style</span>
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</pre></div>
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</div>
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<ul class="simple">
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<li>style = <em>cg</em> or <em>hftn</em> or <em>sd</em> or <em>quickmin</em> or <em>fire</em></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">min_style</span> <span class="n">cg</span>
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<span class="n">min_style</span> <span class="n">fire</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>Choose a minimization algorithm to use when a <a class="reference internal" href="minimize.html"><span class="doc">minimize</span></a>
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command is performed.</p>
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<p>Style <em>cg</em> is the Polak-Ribiere version of the conjugate gradient (CG)
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algorithm. At each iteration the force gradient is combined with the
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previous iteration information to compute a new search direction
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perpendicular (conjugate) to the previous search direction. The PR
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variant affects how the direction is chosen and how the CG method is
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restarted when it ceases to make progress. The PR variant is thought
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to be the most effective CG choice for most problems.</p>
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<p>Style <em>hftn</em> is a Hessian-free truncated Newton algorithm. At each
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iteration a quadratic model of the energy potential is solved by a
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conjugate gradient inner iteration. The Hessian (second derivatives)
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of the energy is not formed directly, but approximated in each
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conjugate search direction by a finite difference directional
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derivative. When close to an energy minimum, the algorithm behaves
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like a Newton method and exhibits a quadratic convergence rate to high
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accuracy. In most cases the behavior of <em>hftn</em> is similar to <em>cg</em>,
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but it offers an alternative if <em>cg</em> seems to perform poorly. This
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style is not affected by the <a class="reference internal" href="min_modify.html"><span class="doc">min_modify</span></a> command.</p>
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<p>Style <em>sd</em> is a steepest descent algorithm. At each iteration, the
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search direction is set to the downhill direction corresponding to the
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force vector (negative gradient of energy). Typically, steepest
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descent will not converge as quickly as CG, but may be more robust in
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some situations.</p>
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<p>Style <em>quickmin</em> is a damped dynamics method described in
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<a class="reference internal" href="#sheppard"><span class="std std-ref">(Sheppard)</span></a>, where the damping parameter is related to the
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projection of the velocity vector along the current force vector for
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each atom. The velocity of each atom is initialized to 0.0 by this
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style, at the beginning of a minimization.</p>
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<p>Style <em>fire</em> is a damped dynamics method described in
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<a class="reference internal" href="#bitzek"><span class="std std-ref">(Bitzek)</span></a>, which is similar to <em>quickmin</em> but adds a variable
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timestep and alters the projection operation to maintain components of
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the velocity non-parallel to the current force vector. The velocity
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of each atom is initialized to 0.0 by this style, at the beginning of
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a minimization.</p>
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<p>Either the <em>quickmin</em> and <em>fire</em> styles are useful in the context of
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nudged elastic band (NEB) calculations via the <a class="reference internal" href="neb.html"><span class="doc">neb</span></a> command.</p>
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<div class="admonition note">
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<p class="first admonition-title">Note</p>
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<p class="last">The damped dynamic minimizers use whatever timestep you have
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defined via the <a class="reference internal" href="timestep.html"><span class="doc">timestep</span></a> command. Often they will
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converge more quickly if you use a timestep about 10x larger than you
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would normally use for dynamics simulations.</p>
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</div>
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<div class="admonition note">
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<p class="first admonition-title">Note</p>
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<p class="last">The <em>quickmin</em> and <em>fire</em> styles do not yet support the use of
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the <a class="reference internal" href="fix_box_relax.html"><span class="doc">fix box/relax</span></a> command or minimizations
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involving the electron radius in <a class="reference internal" href="pair_eff.html"><span class="doc">eFF</span></a> models.</p>
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</div>
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</div>
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<div class="section" id="restrictions">
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<h2>Restrictions</h2>
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<blockquote>
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<div>none</div></blockquote>
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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="min_modify.html"><span class="doc">min_modify</span></a>, <a class="reference internal" href="minimize.html"><span class="doc">minimize</span></a>, <a class="reference internal" href="neb.html"><span class="doc">neb</span></a></p>
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</div>
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<div class="section" id="default">
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<h2>Default</h2>
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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">min_style</span> <span class="n">cg</span>
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</pre></div>
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</div>
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<hr class="docutils" />
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<p id="sheppard"><strong>(Sheppard)</strong> Sheppard, Terrell, Henkelman, J Chem Phys, 128, 134106
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(2008). See ref 1 in this paper for original reference to Qmin in
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Jonsson, Mills, Jacobsen.</p>
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<p id="bitzek"><strong>(Bitzek)</strong> Bitzek, Koskinen, Gahler, Moseler, Gumbsch, Phys Rev Lett,
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97, 170201 (2006).</p>
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