forked from lijiext/lammps
75 lines
2.0 KiB
Plaintext
75 lines
2.0 KiB
Plaintext
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.. index:: compute event/displace
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compute event/displace 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 event/displace threshold
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* ID, group-ID are documented in :doc:`compute <compute>` command
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* event/displace = style name of this compute command
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* threshold = minimum distance anyparticle must move to trigger an event (distance units)
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Examples
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""""""""
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.. parsed-literal::
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compute 1 all event/displace 0.5
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Description
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"""""""""""
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Define a computation that flags an "event" if any particle in the
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group has moved a distance greater than the specified threshold
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distance when compared to a previously stored reference state
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(i.e. the previous event). This compute is typically used in
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conjunction with the :doc:`prd <prd>` and :doc:`tad <tad>` commands,
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to detect if a transition
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to a new minimum energy basin has occurred.
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This value calculated by the compute is equal to 0 if no particle has
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moved far enough, and equal to 1 if one or more particles have moved
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further than the threshold distance.
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.. note::
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If the system is undergoing significant center-of-mass motion,
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due to thermal motion, an external force, or an initial net momentum,
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then this compute will not be able to distinguish that motion from
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local atom displacements and may generate "false postives."
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**Output info:**
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This compute calculates a global scalar (the flag). This value can be
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used by any command that uses a global scalar value from a compute as
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input. See :ref:`Section_howto 15 <howto_15>` for an
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overview of LAMMPS output options.
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The scalar value calculated by this compute is "intensive". The
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scalar value will be a 0 or 1 as explained above.
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Restrictions
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""""""""""""
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This command can only be used if LAMMPS was built with the REPLICA
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package. See the :ref:`Making LAMMPS <start_3>` section
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for more info on packages.
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Related commands
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""""""""""""""""
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:doc:`prd <prd>`, :doc:`tad <tad>`
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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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