freeze command

Warning

GPU support for this command has not been tested and may not work as expected.

Syntax

freeze id command-id particle_group group-id

  • freeze = command name

  • id/command-id = optional keyword-value pair to set the id of the command

  • particle_group/group-id = optional keyword-value pair to apply this command to a specific particle group only

Examples

freeze particle_group bottom
freeze id my_freeze particle_group ice

Description

Zero out the force and torque on a granular particle. This is useful for preventing certain particles from moving in a simulation. The contact models also detect if this fix has been defined and compute interactions between frozen and non-frozen particles appropriately, as if the frozen particle has infinite mass. Note, if using the set_velocity command with a zero vector, this does not happen and the standard particle mass is used for that command.

Output

This fix computes a global 3-vector of forces, which can be accessed by various output commands. This is the total force on the group of particles before the forces on individual atoms are changed by the fix. The vector values calculated by this fix are “extensive”.

Defaults

particle_group: all