fix remove command¶

Syntax¶

fix ID group-ID remove nevery N massrate massrate_value style style_value [delete_below delete_below_value] seed seed_value keyword value ...

• ID, group-ID are documented in fix command

• remove = style name of this fix command

• nevery = obligatory keyword

• N = remove particles every this many timesteps

• massrate = obligatory keyword

• massrate_value = rate at which to remove particles

• massratevariable = alternative keyword to massrate

• massrate_name = name of variable with which to remove particles

• style = obligatory keyword

• style_value = shrink or delete

• delete_below = obligatory keyword if style_value is shrink

• delete_below_value = radius below which particles are removed if style_value is shrink

• seed = obligatory keyword

• seed_value = random # seed (positive integer)

• zero or more keyword/value pairs may be appended

• keywords = region or atomtype or integrated_error or minmass or restart_read or restart_write or monitor_heat or verbose or compress

  region value = region-ID
    region-ID = ID of the region where the particles will be removed
  atomtype value = type
    type = type of atoms to remove
  integrated_error value = yes or no
  minmass value = minimal mass to be removed at once
  restart_read value = yes or no
  restart_write value = yes or no
  monitor_heat value = yes or no
  verbose value = yes or no
  compress value = yes or no

Examples¶

fix 1 all remove nevery 500 massrate 3.5 style delete seed 5143 region del_region atomtype 1
fix 1 all remove nevery 500 massrate 3.5 style shrink delete_below 0.001 seed 7543 region del_region
fix 1 all remove nevery 500 massratevariable removal_rate style delete seed 2137 integrated_error no

Description¶

Remove atoms from the simulation at the specified rate.

For style delete, all atoms belonging to the group are deleted immediately.

For style shrink, atoms belonging to the group are shrunk and get deleted only if their radius is smaller than the value set via delete_below.

The region from which particles are removed can be specified using the region keyword.

The atomtype option allows to restrict deletion to a single type of atoms.

The integrated_error option (default yes) accumulates the mass to be removed over time and subtracts the actually removed mass. If disabled, mass is removed proportionally to the removal rate.

The minmass option allows to specify a minimal value (default 1e-6) for the mass to be removed at once.

The monitor_heat keyword determines if in addition to the removed mass, also the amount of removed heat is stored.

The verbose keyword controls whether statistics about particle removal is output to the screen each time particles are removed.

The restart options (default true) determine whether the fix reads and/or writes restart information.

If the compress keyword is set to yes, then after atoms are removed, the atom IDs are re-assigned so that they run from 1 to the number of atoms in the system. This is not done for molecular systems (see the atom_style command), regardless of the compress setting, since it would foul up the bond connectivity that has already been assigned.

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

If restart_write is not disabled, information about the state of this fix is written to binary restart files. None of the fix_modify options are relevant to this fix. The accumulated removed mass and optionally the heat are stored by this fix for access by various output commands. No parameter of this fix can be used with the start/stop keywords of the run command. This fix is not invoked during energy minimization.

Restrictions¶

Style shrink is not supported for multisphere particles

Related commands¶

delete_atoms

Default¶

The option defaults are monitor_heat = no, verbose = no and compress = yes