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<div class="section" id="create-box-command">
<span id="index-0"></span><h1>create_box command<a class="headerlink" href="#create-box-command" title="Permalink to this headline">¶</a></h1>
<div class="section" id="syntax">
<h2>Syntax<a class="headerlink" href="#syntax" title="Permalink to this headline">¶</a></h2>
<div class="highlight-python"><div class="highlight"><pre>create_box N region-ID
</pre></div>
</div>
<ul class="simple">
<li>N = # of atom types to use in this simulation</li>
<li>region-ID = ID of region to use as simulation domain (optional)</li>
</ul>
</div>
<div class="section" id="examples">
<h2>Examples<a class="headerlink" href="#examples" title="Permalink to this headline">¶</a></h2>
<div class="highlight-python"><div class="highlight"><pre>create_box 2 mybox
create_box 1
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
<p>This command creates a simulation box based on a specified region.
Either a <a class="reference internal" href="region.html"><em>region</em></a> command must first be used to define a
geometric domain and its <em>region-ID</em> must be specified as argument,
or a <code class="xref doc docutils literal"><span class="pre">simulation_domain</span></code> command must be used
first. In the latter case the box defined by the
<code class="xref doc docutils literal"><span class="pre">simulation_domain</span></code> is automatically used if
no <em>region-ID</em> is specified.</p>
<p>The argument N is the number of atom types that will be used in the
simulation.</p>
<p>If the region is not of style <em>prism</em>, then LIGGGHTS(R)-PUBLIC encloses the region
(block, sphere, etc) with an axis-aligned orthogonal bounding box
which becomes the simulation domain.</p>
<p>If the region is of style <em>prism</em>, LIGGGHTS(R)-PUBLIC creates a non-orthogonal
simulation domain shaped as a parallelepiped with triclinic symmetry.
As defined by the <a class="reference internal" href="region.html"><em>region prism</em></a> command, the
parallelepiped has its “origin” at (xlo,ylo,zlo) and is defined by 3
edge vectors starting from the origin given by A = (xhi-xlo,0,0); B =
(xy,yhi-ylo,0); C = (xz,yz,zhi-zlo). <em>Xy,xz,yz</em> can be 0.0 or
positive or negative values and are called “tilt factors” because they
are the amount of displacement applied to faces of an originally
orthogonal box to transform it into the parallelipiped.</p>
<p>A <em>prism</em> region used with the create_box command must have tilt
factors (xy,xz,yz) that do not skew the box more than half the
distance of the parallel box length. For example, if xlo = 2 and xhi
= 12, then the x box length is 10 and the xy tilt factor must be
between -5 and 5. Similarly, both xz and yz must be between
-(xhi-xlo)/2 and +(yhi-ylo)/2. Note that this is not a limitation,
since if the maximum tilt factor is 5 (as in this example), then
configurations with tilt = ..., -15, -5, 5, 15, 25, ... are all
geometrically equivalent.</p>
<p>See <span class="xref std std-ref">Section_howto 12</span> of the doc pages
for a geometric description of triclinic boxes, as defined by LIGGGHTS(R)-PUBLIC,
and how to transform these parameters to and from other commonly used
triclinic representations.</p>
<p>When a prism region is used, the simulation domain must be periodic in
any dimensions with a non-zero tilt factor, as defined by the
<a class="reference internal" href="boundary.html"><em>boundary</em></a> command. I.e. if the xy tilt factor is
non-zero, then both the x and y dimensions must be periodic.
Similarly, x and z must be periodic if xz is non-zero and y and z must
be periodic if yz is non-zero. Also note that if your simulation will
tilt the box, e.g. via the <a class="reference internal" href="fix_deform.html"><em>fix deform</em></a> command, the
simulation box must be defined as triclinic, even if the tilt factors
are initially 0.0.</p>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p class="last">If the system is non-periodic (in a dimension), then
you should not make the lo/hi box dimensions (as defined in your
<a class="reference internal" href="region.html"><em>region</em></a> command) radically smaller/larger than the extent
of the atoms you eventually plan to create, e.g. via the
<a class="reference internal" href="create_atoms.html"><em>create_atoms</em></a> command. For example, if your atoms
extend from 0 to 50, you should not specify the box bounds as -10000
and 10000. This is because LIGGGHTS(R)-PUBLIC uses the specified box size to
layout the 3d grid of processors. A huge (mostly empty) box will be
sub-optimal for performance when using “fixed” boundary conditions
(see the <a class="reference internal" href="boundary.html"><em>boundary</em></a> command). When using “shrink-wrap”
boundary conditions (see the <a class="reference internal" href="boundary.html"><em>boundary</em></a> command), a huge
(mostly empty) box may cause a parallel simulation to lose atoms the
first time that LIGGGHTS(R)-PUBLIC shrink-wraps the box around the atoms.</p>
</div>
</div>
<div class="section" id="restrictions">
<h2>Restrictions<a class="headerlink" href="#restrictions" title="Permalink to this headline">¶</a></h2>
<p>An <a class="reference internal" href="atom_style.html"><em>atom_style</em></a> and one of <a class="reference internal" href="region.html"><em>region</em></a> or
<code class="xref doc docutils literal"><span class="pre">simulation_domain</span></code> must have been previously
defined to use this command.</p>
</div>
<div class="section" id="related-commands">
<h2>Related commands<a class="headerlink" href="#related-commands" title="Permalink to this headline">¶</a></h2>
<p><a class="reference internal" href="create_atoms.html"><em>create_atoms</em></a>, <a class="reference internal" href="region.html"><em>region</em></a>, <code class="xref doc docutils literal"><span class="pre">simulation_domain</span></code></p>
<p><strong>Default:</strong> none</p>
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