125 lines
4.5 KiB
ReStructuredText
125 lines
4.5 KiB
ReStructuredText
.. index:: fix pair/tracker
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fix pair/tracker command
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========================
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Syntax
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""""""
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.. parsed-literal::
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fix ID group-ID pair/tracker N attribute1 attribute2 ... keyword values ...
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* ID, group-ID are documented in :doc:`fix <fix>` command
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* pair/tracker = style name of this fix command
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* N = prepare data for output every this many timesteps
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* one or more attributes may be appended
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.. parsed-literal::
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possible attributes = id1 id2 time/created time/broken time/total
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rmin rave x y z
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.. parsed-literal::
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id1, id2 = IDs of the 2 atoms in each pair interaction
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time/created = the time that the 2 atoms began interacting
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time/broken = the time that the 2 atoms stopped interacting
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time/total = the total time the 2 atoms interacted
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r/min = the minimum radial distance between the 2 atoms during the interaction
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r/ave = the average radial distance between the 2 atoms during the interaction
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x, y, z = the center of mass position of the 2 atoms when they stopped interacting
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* zero or more keyword/value pairs may be appended
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* keyword = *time/min* or *type/include*
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.. parsed-literal::
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*time/min* value = T
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T = minimum interaction time
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*type/include* value = arg1 arg2
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arg = separate lists of types (see below)
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Examples
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""""""""
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.. code-block:: LAMMPS
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fix 1 all pair/tracker 1000 id1 id2 time/min 100
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fix 1 all pair/tracker 1000 time/created time/broken type/include 1 * type/include 2 3,4
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Description
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"""""""""""
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Tracks properties of pairwise interactions between two atoms and records data
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whenever the atoms move beyond the interaction cutoff.
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Must be used in conjunction with :doc:`pair tracker <pair_tracker>`.
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Data is accumulated over a span of *N* timesteps before being deleted.
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The number of datums generated, aggregated across all processors, equals
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the number of broken interactions. Interactions are only included if both
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atoms are included in the specified fix group. Additional filters can be
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applied using the *time/min* or *type/include* keywords described below.
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.. note::
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For extremely long-lived interactions, the calculation of *r/ave* may not be
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correct due to double overflow.
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The *time/min* keyword sets a minimum amount of time that an interaction must
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persist to be included. This setting can be used to censor short-lived interactions.
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The *type/include* keyword filters interactions based on the types of the two atoms.
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Data is only saved for interactions between atoms with types in the two lists.
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Each list consists of a series of type
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ranges separated by commas. The range can be specified as a
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single numeric value, or a wildcard asterisk can be used to specify a range
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of values. This takes the form "\*" or "\*n" or "n\*" or "m\*n". For
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example, if M = the number of atom types, then an asterisk with no numeric
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values means all types from 1 to M. A leading asterisk means all types
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from 1 to n (inclusive). A trailing asterisk means all types from n to M
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(inclusive). A middle asterisk means all types from m to n (inclusive).
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Multiple *type/include* keywords may be added.
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----------
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Restart, fix_modify, run start/stop, minimize info
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"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
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No information about this fix is written to :doc:`binary restart files <restart>`.
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None of the :doc:`fix_modify <fix_modify>` options are
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relevant to this fix.
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No parameter of this fix can be used with the *start/stop* keywords of
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the :doc:`run <run>` command.
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Output info
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"""""""""""
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This compute calculates a local vector or local array depending on the
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number of input values. The length of the vector or number of rows in
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the array is the number of recorded, lost interactions. If a single input is
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specified, a local vector is produced. If two or more inputs are
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specified, a local array is produced where the number of columns = the
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number of inputs. The vector or array can be accessed by any command
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that uses local values from a compute as input. See the :doc:`Howto output <Howto_output>` page for an overview of LAMMPS output
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options.
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The vector or array values will be doubles that correspond to the
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specified attribute.
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Restrictions
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""""""""""""
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Must be used in conjunction with :doc:`pair style tracker <pair_tracker>`.
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This fix is part of the MISC package. It is only enabled if LAMMPS
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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:`pair tracker <pair_tracker>`
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Default
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"""""""
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none
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