102 lines
2.9 KiB
ReStructuredText
102 lines
2.9 KiB
ReStructuredText
.. index:: compute ave/sphere/atom
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.. index:: compute ave/sphere/atom/kk
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compute ave/sphere/atom command
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================================
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Accelerator Variants: *ave/sphere/atom/kk*
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Syntax
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""""""
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.. parsed-literal::
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compute ID group-ID ave/sphere/atom keyword values ...
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* ID, group-ID are documented in :doc:`compute <compute>` command
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* ave/sphere/atom = style name of this compute command
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* one or more keyword/value pairs may be appended
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.. parsed-literal::
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keyword = *cutoff*
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*cutoff* value = distance cutoff
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Examples
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""""""""
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.. code-block:: LAMMPS
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compute 1 all ave/sphere/atom
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compute 1 all ave/sphere/atom cutoff 5.0
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comm_modify cutoff 5.0
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Description
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"""""""""""
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Define a computation that calculates the local density and temperature
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for each atom and neighbors inside a spherical cutoff.
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The optional keyword *cutoff* defines the distance cutoff
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used when searching for neighbors. The default value is the cutoff
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specified by the pair style. If no pair style is defined, then a cutoff
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must be defined using this keyword. If the specified cutoff is larger than
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that of the pair_style plus neighbor skin (or no pair style is defined),
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the *comm_modify cutoff* option must also be set to match that of the
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*cutoff* keyword.
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The neighbor list needed to compute this quantity is constructed each
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time the calculation is performed (i.e. each time a snapshot of atoms
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is dumped). Thus it can be inefficient to compute/dump this quantity
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too frequently.
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.. note::
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If you have a bonded system, then the settings of
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:doc:`special_bonds <special_bonds>` command can remove pairwise
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interactions between atoms in the same bond, angle, or dihedral. This
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is the default setting for the :doc:`special_bonds <special_bonds>`
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command, and means those pairwise interactions do not appear in the
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neighbor list. Because this fix uses the neighbor list, it also means
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those pairs will not be included in the order parameter. This
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difficulty can be circumvented by writing a dump file, and using the
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:doc:`rerun <rerun>` command to compute the order parameter for
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snapshots in the dump file. The rerun script can use a
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:doc:`special_bonds <special_bonds>` command that includes all pairs in
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the neighbor list.
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----------
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.. include:: accel_styles.rst
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----------
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Output info
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"""""""""""
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This compute calculates a per-atom array with two columns: density and temperature.
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These values can be accessed by any command that uses per-atom values
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from a compute as input. See the :doc:`Howto output <Howto_output>` doc
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page for an overview of LAMMPS output options.
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Restrictions
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""""""""""""
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This compute is part of the EXTRA-COMPUTE package. It is only enabled if
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LAMMPS was built with that package. See the :doc:`Build package <Build_package>` page for more info.
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Related commands
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""""""""""""""""
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:doc:`comm_modify <comm_modify>`
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Default
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"""""""
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The option defaults are *cutoff* = pair style cutoff
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