forked from lijiext/lammps
81 lines
2.4 KiB
Plaintext
81 lines
2.4 KiB
Plaintext
.. index:: compute displace/atom
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compute displace/atom command
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=============================
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Syntax
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""""""
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.. parsed-literal::
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compute ID group-ID displace/atom
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* ID, group-ID are documented in :doc:`compute <compute>` command
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* displace/atom = style name of this compute command
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Examples
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""""""""
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.. parsed-literal::
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compute 1 all displace/atom
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Description
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"""""""""""
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Define a computation that calculates the current displacement of each
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atom in the group from its original coordinates, including all effects
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due to atoms passing thru periodic boundaries.
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A vector of four quantites per atom is calculated by this compute.
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The first 3 elements of the vector are the dx,dy,dz displacements.
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The 4th component is the total displacement, i.e. sqrt(dx*dx + dy*dy +
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dz*dz).
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The displacement of an atom is from its original position at the time
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the compute command was issued. The value of the displacement will be
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0.0 for atoms not in the specified compute group.
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.. note::
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Initial coordinates are stored in "unwrapped" form, by using the
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image flags associated with each atom. See the :doc:`dump custom <dump>` command for a discussion of "unwrapped" coordinates.
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See the Atoms section of the :doc:`read_data <read_data>` command for a
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discussion of image flags and how they are set for each atom. You can
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reset the image flags (e.g. to 0) before invoking this compute by
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using the :doc:`set image <set>` command.
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.. note::
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If you want the quantities calculated by this compute to be
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continuous when running from a :doc:`restart file <read_restart>`, then
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you should use the same ID for this compute, as in the original run.
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This is so that the fix this compute creates to store per-atom
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quantities will also have the same ID, and thus be initialized
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correctly with time=0 atom coordinates from the restart file.
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**Output info:**
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This compute calculates a per-atom array with 4 columns, which can be
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accessed by indices 1-4 by any command that uses per-atom values from
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a compute as input. See :ref:`Section_howto 15 <howto_15>` for an overview of LAMMPS output
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options.
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The per-atom array values will be in 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 msd <compute_msd>`, :doc:`dump custom <dump>`, :doc:`fix store/state <fix_store_state>`
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**Default:** none
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.. _lws: http://lammps.sandia.gov
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.. _ld: Manual.html
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.. _lc: Section_commands.html#comm
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