# fix freeze command

## Syntax

    fix ID group-ID freeze

- ID, group-ID are documented in fix command
- freeze = style name of this fix command

## Examples

    fix 2 bottom freeze

## Description

Zero out the force and torque on a granular particle. This is useful for preventing certain particles from moving in a simulation. The granular pair styles 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.

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

No information about this fix is written to binary restart files. None of the fix_modify options are relevant to this fix.

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 atoms before the forces on individual atoms are changed by the fix. The vector values calculated by this fix are “extensive”.

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

There can only be a single freeze fix defined. This is because other the granular pair styles treat frozen particles differently and need to be able to reference a single group to which this fix is applied.

Related commands: none

atom_style sphere

Default: none