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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="newton-command">
<span id="index-0"></span><h1>newton command</h1>
<div class="section" id="syntax">
<h2>Syntax</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">newton</span> <span class="n">flag</span>
<span class="n">newton</span> <span class="n">flag1</span> <span class="n">flag2</span>
</pre></div>
</div>
<ul class="simple">
<li>flag = <em>on</em> or <em>off</em> for both pairwise and bonded interactions</li>
<li>flag1 = <em>on</em> or <em>off</em> for pairwise interactions</li>
<li>flag2 = <em>on</em> or <em>off</em> for bonded interactions</li>
</ul>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">newton</span> <span class="n">off</span>
<span class="n">newton</span> <span class="n">on</span> <span class="n">off</span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>This command turns Newton&#8217;s 3rd law <em>on</em> or <em>off</em> for pairwise and
bonded interactions. For most problems, setting Newton&#8217;s 3rd law to
<em>on</em> means a modest savings in computation at the cost of two times
more communication. Whether this is faster depends on problem size,
force cutoff lengths, a machine&#8217;s compute/communication ratio, and how
many processors are being used.</p>
<p>Setting the pairwise newton flag to <em>off</em> means that if two
interacting atoms are on different processors, both processors compute
their interaction and the resulting force information is not
communicated. Similarly, for bonded interactions, newton <em>off</em> means
that if a bond, angle, dihedral, or improper interaction contains
atoms on 2 or more processors, the interaction is computed by each
processor.</p>
<p>LAMMPS should produce the same answers for any newton flag settings,
except for round-off issues.</p>
<p>With <a class="reference internal" href="run_style.html"><span class="doc">run_style</span></a> <em>respa</em> and only bonded interactions
(bond, angle, etc) computed in the innermost timestep, it may be
faster to turn newton <em>off</em> for bonded interactions, to avoid extra
communication in the innermost loop.</p>
</div>
<div class="section" id="restrictions">
<h2>Restrictions</h2>
<p>The newton bond setting cannot be changed after the simulation box is
defined by a <a class="reference internal" href="read_data.html"><span class="doc">read_data</span></a> or
<a class="reference internal" href="create_box.html"><span class="doc">create_box</span></a> command.</p>
</div>
<div class="section" id="related-commands">
<h2>Related commands</h2>
<p><a class="reference internal" href="run_style.html"><span class="doc">run_style</span></a> respa</p>
</div>
<div class="section" id="default">
<h2>Default</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">newton</span> <span class="n">on</span>
</pre></div>
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