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<div class="section" id="fix-smd-adjust-dt-command">
<span id="index-0"></span><h1>fix smd/adjust_dt command</h1>
<div class="section" id="syntax">
<h2>Syntax</h2>
<pre class="literal-block">
fix ID group-ID smd/adjust_dt arg
</pre>
<ul class="simple">
<li>ID, group-ID are documented in <a class="reference internal" href="fix.html"><span class="doc">fix</span></a> command</li>
<li>smd/adjust_dt = style name of this fix command</li>
<li>arg = <em>s_fact</em></li>
</ul>
<pre class="literal-block">
<em>s_fact</em> = safety factor
</pre>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<pre class="literal-block">
fix 1 all smd/adjust_dt 0.1
</pre>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>The fix calculates a new stable time increment for use with the SMD time integrators.</p>
<p>The stable time increment is based on multiple conditions. For the SPH pair styles, a
CFL criterion (Courant, Friedrichs &amp; Lewy, 1928) is evaluated, which determines the the speed of
sound cannot propagate further than a typical spacing between particles within a single time step to ensure
no information is lost. For the contact pair styles, a linear analysis of the pair potential determines a
stable maximum time step.</p>
<p>This fix inquires the minimum stable time increment across all particles contained in the group for which this
fix is defined. An additional safety factor <em>s_fact</em> is applied to the time increment.</p>
<p>See <a class="reference external" href="USER/smd/SMD_LAMMPS_userguide.pdf">this PDF guide</a> to use Smooth Mach Dynamics in LAMMPS.</p>
<p><strong>Restart, fix_modify, output, run start/stop, minimize info:</strong></p>
<p>Currently, no part of USER-SMD supports restarting nor minimization.</p>
</div>
<div class="section" id="restrictions">
<h2>Restrictions</h2>
<p>This fix is part of the USER-SMD package. It is only enabled if
LAMMPS was built with that package. See the <a class="reference internal" href="Section_start.html#start-3"><span class="std std-ref">Making LAMMPS</span></a>
section for more info.</p>
</div>
<div class="section" id="related-commands">
<h2>Related commands</h2>
<p><a class="reference internal" href="compute_smd_tlsph_dt.html"><span class="doc">smd/tlsph_dt</span></a></p>
<p><strong>Default:</strong> none</p>
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