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<div class="section" id="compute-property-local-command">
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<span id="index-0"></span><h1>compute property/local 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">compute</span> <span class="n">ID</span> <span class="n">group</span><span class="o">-</span><span class="n">ID</span> <span class="nb">property</span><span class="o">/</span><span class="n">local</span> <span class="n">input1</span> <span class="n">input2</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>ID, group-ID are documented in <a class="reference internal" href="compute.html"><span class="doc">compute</span></a> command</li>
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<li>property/local = style name of this compute command</li>
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<li>input = one or more attributes</li>
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</ul>
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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">possible</span> <span class="n">attributes</span> <span class="o">=</span> <span class="n">natom1</span> <span class="n">natom2</span> <span class="n">ntype1</span> <span class="n">ntype2</span>
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<span class="n">patom1</span> <span class="n">patom2</span> <span class="n">ptype1</span> <span class="n">ptype2</span>
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<span class="n">batom1</span> <span class="n">batom2</span> <span class="n">btype</span>
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<span class="n">aatom1</span> <span class="n">aatom2</span> <span class="n">aatom3</span> <span class="n">atype</span>
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<span class="n">datom1</span> <span class="n">datom2</span> <span class="n">datom3</span> <span class="n">dtype</span>
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<span class="n">iatom1</span> <span class="n">iatom2</span> <span class="n">iatom3</span> <span class="n">itype</span>
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</pre></div>
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</div>
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<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">natom1</span><span class="p">,</span> <span class="n">natom2</span> <span class="o">=</span> <span class="n">IDs</span> <span class="n">of</span> <span class="mi">2</span> <span class="n">atoms</span> <span class="ow">in</span> <span class="n">each</span> <span class="n">pair</span> <span class="p">(</span><span class="n">within</span> <span class="n">neighbor</span> <span class="n">cutoff</span><span class="p">)</span>
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<span class="n">ntype1</span><span class="p">,</span> <span class="n">ntype2</span> <span class="o">=</span> <span class="nb">type</span> <span class="n">of</span> <span class="mi">2</span> <span class="n">atoms</span> <span class="ow">in</span> <span class="n">each</span> <span class="n">pair</span> <span class="p">(</span><span class="n">within</span> <span class="n">neighbor</span> <span class="n">cutoff</span><span class="p">)</span>
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<span class="n">patom1</span><span class="p">,</span> <span class="n">patom2</span> <span class="o">=</span> <span class="n">IDs</span> <span class="n">of</span> <span class="mi">2</span> <span class="n">atoms</span> <span class="ow">in</span> <span class="n">each</span> <span class="n">pair</span> <span class="p">(</span><span class="n">within</span> <span class="n">force</span> <span class="n">cutoff</span><span class="p">)</span>
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<span class="n">ptype1</span><span class="p">,</span> <span class="n">ptype2</span> <span class="o">=</span> <span class="nb">type</span> <span class="n">of</span> <span class="mi">2</span> <span class="n">atoms</span> <span class="ow">in</span> <span class="n">each</span> <span class="n">pair</span> <span class="p">(</span><span class="n">within</span> <span class="n">force</span> <span class="n">cutoff</span><span class="p">)</span>
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<span class="n">batom1</span><span class="p">,</span> <span class="n">batom2</span> <span class="o">=</span> <span class="n">IDs</span> <span class="n">of</span> <span class="mi">2</span> <span class="n">atoms</span> <span class="ow">in</span> <span class="n">each</span> <span class="n">bond</span>
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<span class="n">btype</span> <span class="o">=</span> <span class="n">bond</span> <span class="nb">type</span> <span class="n">of</span> <span class="n">each</span> <span class="n">bond</span>
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<span class="n">aatom1</span><span class="p">,</span> <span class="n">aatom2</span><span class="p">,</span> <span class="n">aatom3</span> <span class="o">=</span> <span class="n">IDs</span> <span class="n">of</span> <span class="mi">3</span> <span class="n">atoms</span> <span class="ow">in</span> <span class="n">each</span> <span class="n">angle</span>
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<span class="n">atype</span> <span class="o">=</span> <span class="n">angle</span> <span class="nb">type</span> <span class="n">of</span> <span class="n">each</span> <span class="n">angle</span>
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<span class="n">datom1</span><span class="p">,</span> <span class="n">datom2</span><span class="p">,</span> <span class="n">datom3</span><span class="p">,</span> <span class="n">datom4</span> <span class="o">=</span> <span class="n">IDs</span> <span class="n">of</span> <span class="mi">4</span> <span class="n">atoms</span> <span class="ow">in</span> <span class="n">each</span> <span class="n">dihedral</span>
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<span class="n">dtype</span> <span class="o">=</span> <span class="n">dihedral</span> <span class="nb">type</span> <span class="n">of</span> <span class="n">each</span> <span class="n">dihedral</span>
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<span class="n">iatom1</span><span class="p">,</span> <span class="n">iatom2</span><span class="p">,</span> <span class="n">iatom3</span><span class="p">,</span> <span class="n">iatom4</span> <span class="o">=</span> <span class="n">IDs</span> <span class="n">of</span> <span class="mi">4</span> <span class="n">atoms</span> <span class="ow">in</span> <span class="n">each</span> <span class="n">improper</span>
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<span class="n">itype</span> <span class="o">=</span> <span class="n">improper</span> <span class="nb">type</span> <span class="n">of</span> <span class="n">each</span> <span class="n">improper</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="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">compute</span> <span class="mi">1</span> <span class="nb">all</span> <span class="nb">property</span><span class="o">/</span><span class="n">local</span> <span class="n">btype</span> <span class="n">batom1</span> <span class="n">batom2</span>
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<span class="n">compute</span> <span class="mi">1</span> <span class="nb">all</span> <span class="nb">property</span><span class="o">/</span><span class="n">local</span> <span class="n">atype</span> <span class="n">aatom2</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>Define a computation that stores the specified attributes as local
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data so it can be accessed by other <a class="reference internal" href="Section_howto.html#howto-15"><span class="std std-ref">output commands</span></a>. If the input attributes refer
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to bond information, then the number of datums generated, aggregated
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across all processors, equals the number of bonds in the system.
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Ditto for pairs, angles, etc.</p>
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<p>If multiple input attributes are specified then they must all generate
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the same amount of information, so that the resulting local array has
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the same number of rows for each column. This means that only bond
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attributes can be specified together, or angle attributes, etc. Bond
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and angle attributes can not be mixed in the same compute
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property/local command.</p>
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<p>If the inputs are pair attributes, the local data is generated by
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looping over the pairwise neighbor list. Info about an individual
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pairwise interaction will only be included if both atoms in the pair
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are in the specified compute group. For <em>natom1</em> and <em>natom2</em>, all
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atom pairs in the neighbor list are considered (out to the neighbor
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cutoff = force cutoff + <a class="reference internal" href="neighbor.html"><span class="doc">neighbor skin</span></a>). For <em>patom1</em>
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and <em>patom2</em>, the distance between the atoms must be less than the
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force cutoff distance for that pair to be included, as defined by the
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<a class="reference internal" href="pair_style.html"><span class="doc">pair_style</span></a> and <a class="reference internal" href="pair_coeff.html"><span class="doc">pair_coeff</span></a>
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commands.</p>
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<p>If the inputs are bond, angle, etc attributes, the local data is
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generated by looping over all the atoms owned on a processor and
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extracting bond, angle, etc info. For bonds, info about an individual
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bond will only be included if both atoms in the bond are in the
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specified compute group. Likewise for angles, dihedrals, etc.</p>
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<p>For bonds and angles, a bonds/angles that have been broken by setting
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their bond/angle type to 0 will not be included. Bonds/angles that
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have been turned off (see the <a class="reference internal" href="fix_shake.html"><span class="doc">fix shake</span></a> or
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<a class="reference internal" href="delete_bonds.html"><span class="doc">delete_bonds</span></a> commands) by setting their bond/angle
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type negative are written into the file. This is consistent with the
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<a class="reference internal" href="compute_bond_local.html"><span class="doc">compute bond/local</span></a> and <a class="reference internal" href="compute_angle_local.html"><span class="doc">compute angle/local</span></a> commands</p>
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<p>Note that as atoms migrate from processor to processor, there will be
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no consistent ordering of the entries within the local vector or array
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from one timestep to the next. The only consistency that is
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guaranteed is that the ordering on a particular timestep will be the
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same for local vectors or arrays generated by other compute commands.
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For example, output from the <a class="reference internal" href="compute_bond_local.html"><span class="doc">compute bond/local</span></a> command can be combined with bond
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atom indices from this command and output by the <a class="reference internal" href="dump.html"><span class="doc">dump local</span></a> command in a consistent way.</p>
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<p>The <em>natom1</em> and <em>natom2</em>, or <em>patom1</em> and <em>patom2</em> attributes refer
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to the atom IDs of the 2 atoms in each pairwise interaction computed
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by the <a class="reference internal" href="pair_style.html"><span class="doc">pair_style</span></a> command. The <em>ntype1</em> and
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<em>ntype2</em>, or <em>ptype1</em> and <em>ptype2</em> attributes refer to the atom types
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of the 2 atoms in each pairwise interaction.</p>
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<div class="admonition note">
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<p class="first admonition-title">Note</p>
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<p class="last">For pairs, if two atoms I,J are involved in 1-2, 1-3, 1-4
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interactions within the molecular topology, their pairwise interaction
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may be turned off, and thus they may not appear in the neighbor list,
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and will not be part of the local data created by this command. More
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specifically, this may be true of I,J pairs with a weighting factor of
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0.0; pairs with a non-zero weighting factor are included. The
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weighting factors for 1-2, 1-3, and 1-4 pairwise interactions are set
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by the <a class="reference internal" href="special_bonds.html"><span class="doc">special_bonds</span></a> command.</p>
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</div>
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<p>The <em>batom1</em> and <em>batom2</em> attributes refer to the atom IDs of the 2
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atoms in each <a class="reference internal" href="bond_style.html"><span class="doc">bond</span></a>. The <em>btype</em> attribute refers to
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the type of the bond, from 1 to Nbtypes = # of bond types. The number
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of bond types is defined in the data file read by the
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<a class="reference internal" href="read_data.html"><span class="doc">read_data</span></a> command.</p>
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<p>The attributes that start with “a”, “d”, “i”, refer to similar values
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for <a class="reference internal" href="angle_style.html"><span class="doc">angles</span></a>, <a class="reference internal" href="dihedral_style.html"><span class="doc">dihedrals</span></a>, and
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<a class="reference internal" href="improper_style.html"><span class="doc">impropers</span></a>.</p>
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<p><strong>Output info:</strong></p>
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<p>This compute calculates a local vector or local array depending on the
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number of input values. The length of the vector or number of rows in
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the array is the number of bonds, angles, etc. If a single input is
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specified, a local vector is produced. If two or more inputs are
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specified, a local array is produced where the number of columns = the
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number of inputs. The vector or array can be accessed by any command
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that uses local values from a compute as input. See <a class="reference internal" href="Section_howto.html#howto-15"><span class="std std-ref">this section</span></a> for an overview of LAMMPS output
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options.</p>
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<p>The vector or array values will be integers that correspond to the
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specified attribute.</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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<blockquote>
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<div>none</div></blockquote>
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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="dump.html"><span class="doc">dump local</span></a>, <a class="reference internal" href="compute_reduce.html"><span class="doc">compute reduce</span></a></p>
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<p><strong>Default:</strong> none</p>
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