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