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compute nparticles/tracer/region command

Syntax:

compute ID group-ID nparticles/tracer/region

ID, group-ID are documented in compute command

nparticles/tracer/region = style name of this compute command

region_count = obligatory keyword

region-ID = ID of region atoms must be in to be counted

tracer = obligatory keyword

tracer-ID = ID of a fix of type fix property/atom/tracer

zero or more keyword/value pairs may be appended to args

keyword = periodic or reset_marker

  periodic value = dim image
    dim = x or y or z
    image = image that a particle has to be in to be counted (any integer number or all)
  reset_marker value = yes or no
    yes = un-mark particles after counting them
    no = do not un-mark particles after counting them

Examples:

compute nparticles all nparticles/tracer/region region_count count tracer tr periodic z -1

Description:

Define a computation that calculates the number and mass of marked and un-marked particles that are in the region speficied via the region_count keyword. Particles have to be in the group "group-ID" to be counted.

Note that only particles marked by a fix property/atom/tracer or fix property/atom/tracer/stream command are counted - therefore, a valid ID of such a fix has to be provided via the tracer keyword.

The reset_marker keyword controls if particles are un-marked (default) after they have been counted once by this command.

IMPORTANT NOTE: If multiple compute nparticles/tracer/region commands are operating on the same fix property/atom/tracer commands, and the first compute resets the marker value, the second compute will not count them.

With the periodic keyword, you can restrict counting/unmarking to particles which are in a specified image in a periodic simulation. For example, using

periodic z +2

means that particles are only counted if they are in z-image #2. By default, all particles are counted/unmarked regardless in which periodic image they are.

IMPORTANT NOTE: Currently, this command only supports one periodic boundary restriction via the periodic keyword. If keyword periodic is used multiple times, the last setting will be applied.

Output info:

This this compute calculates a global vector containing the following information (the number in brackets corresponds to the vector id):

(1) total number of (marked + un-marked) particles in region

(2) number of marked particles in region

(3) total mass of (marked + un-marked) particles in region

(4) mass of marked particles in region

See this section for an overview of LIGGGHTS(R)-PUBLIC output options.

Restrictions:

Currently, only one periodic restriction via the periodic keyword can be used.

Related commands:

fix property/atom/tracer

Default: reset_marker = yes, periodic is off per default