fix multisphere/break command — LIGGGHTS v3.X documentation

# fix multisphere/break command

## Syntax

    fix ID group-ID multisphere/break keyword value ...

- ID, group-ID are documented in fix command
- multisphere/break = style name of this fix command
- keywords = same as for fix multisphere, in addition: trigger_threshold and trigger_timeStep and trigger_name (or the deprecated:trigger_fixName)

    trigger_threshold value = x in units matching that of trigger_fixName
      this allows the user the specify a threshold value that will be compared with the per-atom value provided by trigger_fixName, e.g., the residence time in a region (e.g., computed via a fix property/atom/tracer/residencetime). if the threshold is exceeded, the multisphere particle will break.
    trigger_timeStep value = x in steps
      this allows the user to activate the fix after a predefined number of steps.
    trigger_name
      the user must specify a reference to a fix property/atom or variable of style atom that is used as the trigger value.

    trigger_fixName (deprecated!)
      the user must specify the name of the fix that specified per-atom information that is used as the trigger value.

## Examples

    fix integr  grpMulti1  multisphere/break allow_group_and_set yes trigger_threshold 0.1 trigger_timeStep 0 trigger_name f_resTimeMill
    fix integr  grpMulti2  multisphere/break allow_group_and_set yes trigger_threshold 1 trigger_timeStep 0 trigger_name f_pressure**1**
    fix integr  grpMulti3  multisphere/break allow_group_and_set yes trigger_threshold 50 trigger_timeStep 10 trigger_name v_myAtomVariable

## Description

The integration that is performed by this command is euqivalent to fix_multisphere. However, the user can trigger breakage events, which will destroy the “body” the atoms are in. The trigger is imiplemented such that in case the trigger value of one atom in a body exceeds the threshold value, the whole body will break. There are no fragments: all atoms that constitutea body will be released upon breakage.

Note

the atoms in a body MUST NOT overlap, since the atoms are simply released from the body without adjusting their size or their position.

Note

A integrator for the spheres needs to be available (e.g. fix nve/sphere) otherwise the multisphere will fragment but no futher integration of the particles will occur

## Restart, fix_modify, output, run start/stop, minimize info

Same as for fix_multisphere.

## Restrictions

Same as for fix_multisphere.

## Related commands

fix_multisphere

Default: none