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<li class="toctree-l1"><a class="reference internal" href="Section_intro.html">1. Introduction</a></li>
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<li>read_dump command</li>
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<div class="section" id="read-dump-command">
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<span id="index-0"></span><h1>read_dump 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">read_dump</span> <span class="n">file</span> <span class="n">Nstep</span> <span class="n">field1</span> <span class="n">field2</span> <span class="o">...</span> <span class="n">keyword</span> <span class="n">values</span> <span class="o">...</span>
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</pre></div>
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</div>
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<ul class="simple">
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<li>file = name of dump file to read</li>
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<li>Nstep = snapshot timestep to read from file</li>
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<li>one or more fields may be appended</li>
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</ul>
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<pre class="literal-block">
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field = <em>x</em> or <em>y</em> or <em>z</em> or <em>vx</em> or <em>vy</em> or <em>vz</em> or <em>q</em> or <em>ix</em> or <em>iy</em> or <em>iz</em>
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<em>x</em>,<em>y</em>,<em>z</em> = atom coordinates
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<em>vx</em>,<em>vy</em>,<em>vz</em> = velocity components
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<em>q</em> = charge
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<em>ix</em>,<em>iy</em>,<em>iz</em> = image flags in each dimension
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</pre>
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<ul class="simple">
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<li>zero or more keyword/value pairs may be appended</li>
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<li>keyword = <em>box</em> or <em>replace</em> or <em>purge</em> or <em>trim</em> or <em>add</em> or <em>label</em> or <em>scaled</em> or <em>wrapped</em> or <em>format</em></li>
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</ul>
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<pre class="literal-block">
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<em>box</em> value = <em>yes</em> or <em>no</em> = replace simulation box with dump box
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<em>replace</em> value = <em>yes</em> or <em>no</em> = overwrite atoms with dump atoms
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<em>purge</em> value = <em>yes</em> or <em>no</em> = delete all atoms before adding dump atoms
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<em>trim</em> value = <em>yes</em> or <em>no</em> = trim atoms not in dump snapshot
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<em>add</em> value = <em>yes</em> or <em>no</em> = add new dump atoms to system
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<em>label</em> value = field column
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field = one of the listed fields or <em>id</em> or <em>type</em>
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column = label on corresponding column in dump file
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<em>scaled</em> value = <em>yes</em> or <em>no</em> = coords in dump file are scaled/unscaled
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<em>wrapped</em> value = <em>yes</em> or <em>no</em> = coords in dump file are wrapped/unwrapped
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<em>format</em> values = format of dump file, must be last keyword if used
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<em>native</em> = native LAMMPS dump file
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<em>xyz</em> = XYZ file
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<em>molfile</em> style path = VMD molfile plugin interface
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style = <em>dcd</em> or <em>xyz</em> or others supported by molfile plugins
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path = optional path for location of molfile plugins
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</pre>
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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">read_dump</span> <span class="n">dump</span><span class="o">.</span><span class="n">file</span> <span class="mi">5000</span> <span class="n">x</span> <span class="n">y</span> <span class="n">z</span>
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<span class="n">read_dump</span> <span class="n">dump</span><span class="o">.</span><span class="n">xyz</span> <span class="mi">5</span> <span class="n">x</span> <span class="n">y</span> <span class="n">z</span> <span class="n">box</span> <span class="n">no</span> <span class="nb">format</span> <span class="n">xyz</span>
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<span class="n">read_dump</span> <span class="n">dump</span><span class="o">.</span><span class="n">xyz</span> <span class="mi">10</span> <span class="n">x</span> <span class="n">y</span> <span class="n">z</span> <span class="n">box</span> <span class="n">no</span> <span class="nb">format</span> <span class="n">molfile</span> <span class="n">xyz</span> <span class="s2">"../plugins"</span>
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<span class="n">read_dump</span> <span class="n">dump</span><span class="o">.</span><span class="n">dcd</span> <span class="mi">0</span> <span class="n">x</span> <span class="n">y</span> <span class="n">z</span> <span class="n">box</span> <span class="n">yes</span> <span class="nb">format</span> <span class="n">molfile</span> <span class="n">dcd</span>
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<span class="n">read_dump</span> <span class="n">dump</span><span class="o">.</span><span class="n">file</span> <span class="mi">1000</span> <span class="n">x</span> <span class="n">y</span> <span class="n">z</span> <span class="n">vx</span> <span class="n">vy</span> <span class="n">vz</span> <span class="n">box</span> <span class="n">yes</span> <span class="nb">format</span> <span class="n">molfile</span> <span class="n">lammpstrj</span> <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">local</span><span class="o">/</span><span class="n">lib</span><span class="o">/</span><span class="n">vmd</span><span class="o">/</span><span class="n">plugins</span><span class="o">/</span><span class="n">LINUXAMD64</span><span class="o">/</span><span class="n">plugins</span><span class="o">/</span><span class="n">molfile</span>
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<span class="n">read_dump</span> <span class="n">dump</span><span class="o">.</span><span class="n">file</span> <span class="mi">5000</span> <span class="n">x</span> <span class="n">y</span> <span class="n">vx</span> <span class="n">vy</span> <span class="n">trim</span> <span class="n">yes</span>
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<span class="n">read_dump</span> <span class="o">../</span><span class="n">run7</span><span class="o">/</span><span class="n">dump</span><span class="o">.</span><span class="n">file</span><span class="o">.</span><span class="n">gz</span> <span class="mi">10000</span> <span class="n">x</span> <span class="n">y</span> <span class="n">z</span> <span class="n">box</span> <span class="n">yes</span>
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<span class="n">read_dump</span> <span class="n">dump</span><span class="o">.</span><span class="n">xyz</span> <span class="mi">10</span> <span class="n">x</span> <span class="n">y</span> <span class="n">z</span> <span class="n">box</span> <span class="n">no</span> <span class="nb">format</span> <span class="n">molfile</span> <span class="n">xyz</span> <span class="o">../</span><span class="n">plugins</span>
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<span class="n">read_dump</span> <span class="n">dump</span><span class="o">.</span><span class="n">dcd</span> <span class="mi">0</span> <span class="n">x</span> <span class="n">y</span> <span class="n">z</span> <span class="nb">format</span> <span class="n">molfile</span> <span class="n">dcd</span>
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<span class="n">read_dump</span> <span class="n">dump</span><span class="o">.</span><span class="n">file</span> <span class="mi">1000</span> <span class="n">x</span> <span class="n">y</span> <span class="n">z</span> <span class="n">vx</span> <span class="n">vy</span> <span class="n">vz</span> <span class="nb">format</span> <span class="n">molfile</span> <span class="n">lammpstrj</span> <span class="o">/</span><span class="n">usr</span><span class="o">/</span><span class="n">local</span><span class="o">/</span><span class="n">lib</span><span class="o">/</span><span class="n">vmd</span><span class="o">/</span><span class="n">plugins</span><span class="o">/</span><span class="n">LINUXAMD64</span><span class="o">/</span><span class="n">plugins</span><span class="o">/</span><span class="n">molfile</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>Read atom information from a dump file to overwrite the current atom
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coordinates, and optionally the atom velocities and image flags and
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the simluation box dimensions. This is useful for restarting a run
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from a particular snapshot in a dump file. See the
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<a class="reference internal" href="read_restart.html"><span class="doc">read_restart</span></a> and <a class="reference internal" href="read_data.html"><span class="doc">read_data</span></a>
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commands for alternative methods to do this. Also see the
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<a class="reference internal" href="rerun.html"><span class="doc">rerun</span></a> command for a means of reading multiple snapshots
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from a dump file.</p>
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<p>Note that a simulation box must already be defined before using the
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read_dump command. This can be done by the
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<a class="reference internal" href="create_box.html"><span class="doc">create_box</span></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="read_restart.html"><span class="doc">read_restart</span></a> commands. The read_dump command can
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reset the simulation box dimensions, as explained below.</p>
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<p>Also note that reading per-atom information from a dump snapshot is
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limited to the atom coordinates, velocities and image flags, as
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explained below. Other atom properties, which may be necessary to run
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a valid simulation, such as atom charge, or bond topology information
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for a molecular system, are not read from (or even contained in) dump
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files. Thus this auxiliary information should be defined in the usual
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way, e.g. in a data file read in by a <a class="reference internal" href="read_data.html"><span class="doc">read_data</span></a>
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command, before using the read_dump command, or by the <a class="reference internal" href="set.html"><span class="doc">set</span></a>
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command, after the dump snapshot is read.</p>
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<hr class="docutils" />
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<p>If the dump filename specified as <em>file</em> ends with ”.gz”, the dump
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file is read in gzipped format. You cannot (yet) read a dump file
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that was written in binary format with a ”.bin” suffix, or to multiple
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files via the “%” option in the dump file name. See the
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<a class="reference internal" href="dump.html"><span class="doc">dump</span></a> command for details.</p>
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<p>The format of the dump file is selected through the <em>format</em> keyword.
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If specified, it must be the last keyword used, since all remaining
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arguments are passed on to the dump reader. The <em>native</em> format is
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for native LAMMPS dump files, written with a <a class="reference internal" href="dump.html"><span class="doc">dump atom</span></a> or
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<a class="reference internal" href="dump.html"><span class="doc">dump custom</span></a> command. The <em>xyz</em> format is for generic XYZ
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formatted dump files. These formats take no additional values.</p>
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<p>The <em>molfile</em> format supports reading data through using the <a class="reference external" href="vmd">VMD</a>
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molfile plugin interface. This dump reader format is only available,
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if the USER-MOLFILE package has been installed when compiling
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LAMMPS.</p>
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<p>The <em>molfile</em> format takes one or two additional values. The <em>style</em>
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value determines the file format to be used and can be any format that
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the molfile plugins support, such as DCD or XYZ. Note that DCD dump
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files can be written by LAMMPS via the <a class="reference internal" href="dump.html"><span class="doc">dump dcd</span></a> command.
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The <em>path</em> value specifies a list of directories which LAMMPS will
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search for the molfile plugins appropriate to the specified <em>style</em>.
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The syntax of the <em>path</em> value is like other search paths: it can
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contain multiple directories separated by a colon (or semi-colon on
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windows). The <em>path</em> keyword is optional and defaults to ”.”,
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i.e. the current directory.</p>
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<p>Support for other dump format readers may be added in the future.</p>
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<hr class="docutils" />
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<p>Global information is first read from the dump file, namely timestep
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and box information.</p>
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<p>The dump file is scanned for a snapshot with a time stamp that matches
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the specified <em>Nstep</em>. This means the LAMMPS timestep the dump file
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snapshot was written on for the <em>native</em> format. Note that the <em>xyz</em>
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and <em>molfile</em> formats do not store the timestep. For these formats,
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timesteps are numbered logically, in a sequential manner, starting
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from 0. Thus to access the 10th snapshot in an <em>xyz</em> or <em>mofile</em>
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formatted dump file, use <em>Nstep</em> = 9.</p>
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<p>The dimensions of the simulation box for the selected snapshot are
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also read; see the <em>box</em> keyword discussion below. For the <em>native</em>
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format, an error is generated if the snapshot is for a triclinic box
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and the current simulation box is orthogonal or vice versa. A warning
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will be generated if the snapshot box boundary conditions (periodic,
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shrink-wrapped, etc) do not match the current simulation boundary
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conditions, but the boundary condition information in the snapshot is
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otherwise ignored. See the “boundary” command for more details.</p>
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<p>For the <em>xyz</em> format, no information about the box is available, so
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you must set the <em>box</em> flag to <em>no</em>. See details below.</p>
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<p>For the <em>molfile</em> format, reading simulation box information is
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typically supported, but the location of the simulation box origin is
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lost and no explicit information about periodicity or
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orthogonal/triclinic box shape is available. The USER-MOLFILE package
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makes a best effort to guess based on heuristics, but this may not
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always work perfectly.</p>
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<hr class="docutils" />
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<p>Per-atom information from the dump file snapshot is then read from the
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dump file snapshot. This corresponds to the specified <em>fields</em> listed
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in the read_dump command. It is an error to specify a z-dimension
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field, namely <em>z</em>, <em>vz</em>, or <em>iz</em>, for a 2d simulation.</p>
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<p>For dump files in <em>native</em> format, each column of per-atom data has a
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text label listed in the file. A matching label for each field must
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appear, e.g. the label “vy” for the field <em>vy</em>. For the <em>x</em>, <em>y</em>, <em>z</em>
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fields any of the following labels are considered a match:</p>
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<pre class="literal-block">
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x, xs, xu, xsu for field <em>x</em>
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y, ys, yu, ysu for field <em>y</em>
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z, zs, zu, zsu for field <em>z</em>
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</pre>
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<p>The meaning of xs (scaled), xu (unwrapped), and xsu (scaled and
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unwrapped) is explained on the <a class="reference internal" href="dump.html"><span class="doc">dump</span></a> command doc page.
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These labels are searched for in the list of column labels in the dump
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file, in order, until a match is found.</p>
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<p>The dump file must also contain atom IDs, with a column label of “id”.</p>
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<p>If the <em>add</em> keyword is specified with a value of <em>yes</em>, as discussed
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below, the dump file must contain atom types, with a column label of
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“type”.</p>
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<p>If a column label you want to read from the dump file is not a match
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to a specified field, the <em>label</em> keyword can be used to specify the
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specific column label from the dump file to associate with that field.
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An example is if a time-averaged coordinate is written to the dump
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file via the <a class="reference internal" href="fix_ave_atom.html"><span class="doc">fix ave/atom</span></a> command. The column
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will then have a label corresponding to the fix-ID rather than “x” or
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“xs”. The <em>label</em> keyword can also be used to specify new column
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labels for fields <em>id</em> and <em>type</em>.</p>
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<p>For dump files in <em>xyz</em> format, only the <em>x</em>, <em>y</em>, and <em>z</em> fields are
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supported. The dump file does not store atom IDs, so these are
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assigned consecutively to the atoms as they appear in the dump file,
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starting from 1. Thus you should insure that order of atoms is
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consistent from snapshot to snapshot in the the XYZ dump file. See
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the <a class="reference internal" href="dump_modify.html"><span class="doc">dump_modify sort</span></a> command if the XYZ dump file
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was written by LAMMPS.</p>
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<p>For dump files in <em>molfile</em> format, the <em>x</em>, <em>y</em>, <em>z</em>, <em>vx</em>, <em>vy</em>, and
|
|
<em>vz</em> fields can be specified. However, not all molfile formats store
|
|
velocities, or their respective plugins may not support reading of
|
|
velocities. The molfile dump files do not store atom IDs, so these
|
|
are assigned consecutively to the atoms as they appear in the dump
|
|
file, starting from 1. Thus you should insure that order of atoms are
|
|
consistent from snapshot to snapshot in the the molfile dump file.
|
|
See the <a class="reference internal" href="dump_modify.html"><span class="doc">dump_modify sort</span></a> command if the dump file
|
|
was written by LAMMPS.</p>
|
|
<hr class="docutils" />
|
|
<p>Information from the dump file snapshot is used to overwrite or
|
|
replace properties of the current system. There are various options
|
|
for how this is done, determined by the specified fields and optional
|
|
keywords.</p>
|
|
<p>The timestep of the snapshot becomes the current timestep for the
|
|
simulation. See the <a class="reference internal" href="reset_timestep.html"><span class="doc">reset_timestep</span></a> command if
|
|
you wish to change this after the dump snapshot is read.</p>
|
|
<p>If the <em>box</em> keyword is specified with a <em>yes</em> value, then the current
|
|
simulation box dimensions are replaced by the dump snapshot box
|
|
dimensions. If the <em>box</em> keyword is specified with a <em>no</em> value, the
|
|
current simulatoin box is unchanged.</p>
|
|
<p>If the <em>purge</em> keyword is specified with a <em>yes</em> value, then all
|
|
current atoms in the system are deleted before any of the operations
|
|
invoked by the <em>replace</em>, <em>trim</em>, or <em>add</em> keywords take place.</p>
|
|
<p>If the <em>replace</em> keyword is specified with a <em>yes</em> value, then atoms
|
|
with IDs that are in both the current system and the dump snapshot
|
|
have their properties overwritten by field values. If the <em>replace</em>
|
|
keyword is specified with a <em>no</em> value, atoms with IDs that are in
|
|
both the current system and the dump snapshot are not modified.</p>
|
|
<p>If the <em>trim</em> keyword is specified with a <em>yes</em> value, then atoms with
|
|
IDs that are in the current system but not in the dump snapshot are
|
|
deleted. These atoms are unaffected if the <em>trim</em> keyword is
|
|
specified with a <em>no</em> value.</p>
|
|
<p>If the <em>add</em> keyword is specified with a <em>yes</em> value, then atoms with
|
|
IDs that are in the dump snapshot, but not in the current system are
|
|
added to the system. These dump atoms are ignored if the <em>add</em>
|
|
keyword is specified with a <em>no</em> value.</p>
|
|
<p>Note that atoms added via the <em>add</em> keyword will have only the
|
|
attributes read from the dump file due to the <em>field</em> arguments. If
|
|
<em>x</em> or <em>y</em> or <em>z</em> is not specified as a field, a value of 0.0 is used
|
|
for added atoms. Added atoms must have an atom type, so this value
|
|
must appear in the dump file.</p>
|
|
<p>Any other attributes (e.g. charge or particle diameter for spherical
|
|
particles) will be set to default values, the same as if the
|
|
<a class="reference internal" href="create_atoms.html"><span class="doc">create_atoms</span></a> command were used.</p>
|
|
<p>Note that atom IDs are not preserved for new dump snapshot atoms added
|
|
via the <em>add</em> keyword. The procedure for assigning new atom IDS to
|
|
added atoms is the same as is described for the
|
|
<a class="reference internal" href="create_atoms.html"><span class="doc">create_atoms</span></a> command.</p>
|
|
<hr class="docutils" />
|
|
<p>Atom coordinates read from the dump file are first converted into
|
|
unscaled coordinates, relative to the box dimensions of the snapshot.
|
|
These coordinates are then be assigned to an existing or new atom in
|
|
the current simulation. The coordinates will then be remapped to the
|
|
simulation box, whether it is the original box or the dump snapshot
|
|
box. If periodic boundary conditions apply, this means the atom will
|
|
be remapped back into the simulation box if necessary. If shrink-wrap
|
|
boundary conditions apply, the new coordinates may change the
|
|
simulation box dimensions. If fixed boundary conditions apply, the
|
|
atom will be lost if it is outside the simulation box.</p>
|
|
<p>For <em>native</em> format dump files, the 3 xyz image flags for an atom in
|
|
the dump file are set to the corresponding values appearing in the
|
|
dump file if the <em>ix</em>, <em>iy</em>, <em>iz</em> fields are specified. If not
|
|
specified, the image flags for replaced atoms are not changed and
|
|
image flags for new atoms are set to default values. If coordinates
|
|
read from the dump file are in unwrapped format (e.g. <em>xu</em>) then the
|
|
image flags for read-in atoms are also set to default values. The
|
|
remapping procedure described in the previous paragraph will then
|
|
change images flags for all atoms (old and new) if periodic boundary
|
|
conditions are applied to remap an atom back into the simulation box.</p>
|
|
<div class="admonition note">
|
|
<p class="first admonition-title">Note</p>
|
|
<p class="last">If you get a warning about inconsistent image flags after
|
|
reading in a dump snapshot, it means one or more pairs of bonded atoms
|
|
now have inconsistent image flags. As discussed in <a class="reference internal" href="Section_errors.html"><span class="doc">Section errors</span></a> this may or may not cause problems for
|
|
subsequent simulations, One way this can happen is if you read image
|
|
flag fields from the dump file but do not also use the dump file box
|
|
parameters.</p>
|
|
</div>
|
|
<p>LAMMPS knows how to compute unscaled and remapped coordinates for the
|
|
snapshot column labels discussed above, e.g. <em>x</em>, <em>xs</em>, <em>xu</em>, <em>xsu</em>.
|
|
If another column label is assigned to the <em>x</em> or <em>y</em> or <em>z</em> field via
|
|
the <em>label</em> keyword, e.g. for coordinates output by the <a class="reference internal" href="fix_ave_atom.html"><span class="doc">fix ave/atom</span></a> command, then LAMMPS needs to know whether
|
|
the coordinate information in the dump file is scaled and/or wrapped.
|
|
This can be set via the <em>scaled</em> and <em>wrapped</em> keywords. Note that
|
|
the value of the <em>scaled</em> and <em>wrapped</em> keywords is ignored for fields
|
|
<em>x</em> or <em>y</em> or <em>z</em> if the <em>label</em> keyword is not used to assign a
|
|
column label to that field.</p>
|
|
<p>The scaled/unscaled and wrapped/unwrapped setting must be identical
|
|
for any of the <em>x</em>, <em>y</em>, <em>z</em> fields that are specified. Thus you
|
|
cannot read <em>xs</em> and <em>yu</em> from the dump file. Also, if the dump file
|
|
coordinates are scaled and the simulation box is triclinic, then all 3
|
|
of the <em>x</em>, <em>y</em>, <em>z</em> fields must be specified, since they are all
|
|
needed to generate absolute, unscaled coordinates.</p>
|
|
</div>
|
|
<hr class="docutils" />
|
|
<div class="section" id="restrictions">
|
|
<h2>Restrictions</h2>
|
|
<p>To read gzipped dump files, you must compile LAMMPS with the
|
|
-DLAMMPS_GZIP option - see the <a class="reference internal" href="Section_start.html#start-2"><span class="std std-ref">Making LAMMPS</span></a> section of the documentation.</p>
|
|
<p>The <em>molfile</em> dump file formats are part of the USER-MOLFILE package.
|
|
They are only enabled if LAMMPS was built with that packages. 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="dump.html"><span class="doc">dump</span></a>, <a class="reference internal" href="dump_molfile.html"><span class="doc">dump molfile</span></a>,
|
|
<a class="reference internal" href="read_data.html"><span class="doc">read_data</span></a>, <a class="reference internal" href="read_restart.html"><span class="doc">read_restart</span></a>,
|
|
<a class="reference internal" href="rerun.html"><span class="doc">rerun</span></a></p>
|
|
</div>
|
|
<div class="section" id="default">
|
|
<h2>Default</h2>
|
|
<p>The option defaults are box = yes, replace = yes, purge = no, trim =
|
|
no, add = no, scaled = no, wrapped = yes, and format = native.</p>
|
|
</div>
|
|
</div>
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