68 lines
1.6 KiB
ReStructuredText
68 lines
1.6 KiB
ReStructuredText
.. index:: compute com
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compute com command
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===================
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Syntax
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""""""
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.. code-block:: LAMMPS
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compute ID group-ID com
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* ID, group-ID are documented in :doc:`compute <compute>` command
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* com = style name of this compute command
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Examples
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""""""""
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.. code-block:: LAMMPS
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compute 1 all com
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Description
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"""""""""""
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Define a computation that calculates the center-of-mass of the group
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of atoms, including all effects due to atoms passing through periodic
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boundaries.
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A vector of three quantities is calculated by this compute, which
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are the :math:`(x,y,z)` coordinates of the center of mass.
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.. note::
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The coordinates of an atom contribute to the center-of-mass in
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"unwrapped" form, by using the image flags associated with each atom.
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See the :doc:`dump custom <dump>` command for a discussion of
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"unwrapped" coordinates. See the Atoms section of the
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:doc:`read_data <read_data>` command for a discussion of image flags and
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how they are set for each atom. You can reset the image flags
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(e.g., to 0) before invoking this compute by using the
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:doc:`set image <set>` command.
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Output info
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"""""""""""
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This compute calculates a global vector of length 3, which can be
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accessed by indices 1--3 by any command that uses global vector 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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The vector values are "intensive". The vector values will be in
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distance :doc:`units <units>`.
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Restrictions
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""""""""""""
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none
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Related commands
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""""""""""""""""
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:doc:`compute com/chunk <compute_com_chunk>`
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Default
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"""""""
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none
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