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lammps/doc/html/_sources/compute_com.txt
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compute_com.txt
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.. index:: compute com
compute com command
===================
Syntax
""""""
.. parsed-literal::
compute ID group-ID com
* ID, group-ID are documented in :doc:`compute <compute>` command
* com = style name of this compute command
Examples
""""""""
.. parsed-literal::
compute 1 all com
Description
"""""""""""
Define a computation that calculates the center-of-mass of the group
of atoms, including all effects due to atoms passing thru periodic
boundaries.
A vector of three quantites is calculated by this compute, which
are the x,y,z coordinates of the center of mass.
.. note::
The coordinates of an atom contribute to the center-of-mass in
"unwrapped" form, by using the image flags associated with each atom.
See the :doc:`dump custom <dump>` command for a discussion of
"unwrapped" coordinates. See the Atoms section of the
:doc:`read_data <read_data>` command for a discussion of image flags and
how they are set for each atom. You can reset the image flags
(e.g. to 0) before invoking this compute by using the :doc:`set image <set>` command.
**Output info:**
This compute calculates a global vector of length 3, which can be
accessed by indices 1-3 by any command that uses global vector values
from a compute as input. See :ref:`this section <howto_15>` for an overview of LAMMPS output
options.
The vector values are "intensive". The vector values will be in
distance :doc:`units <units>`.
Restrictions
""""""""""""
none
Related commands
""""""""""""""""
:doc:`compute com/chunk <compute_com_chunk>`
**Default:** none
.. _lws: http://lammps.sandia.gov
.. _ld: Manual.html
.. _lc: Section_commands.html#comm
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