Syntax:
fix ID group-ID momentum N keyword values ...
linear values = xflag yflag zflag xflag,yflag,zflag = 0/1 to exclude/include each dimension angular values = none
Examples:
fix 1 all momentum 1 linear 1 1 0 angular
Description:
Zero the linear and/or angular momentum of the group of atoms every N timesteps by adjusting the velocities of the atoms.
If the linear keyword is used, the linear momentum is zeroed by subtracting the center-of-mass velocity of the group from each atom. This does not change the relative velocity of any pair of atoms. One or more dimensions can be excluded from this operation by setting the corresponding flag to 0.
If the angular keyword is used, the angular momentum is zeroed by subtracting a rotational component from each atom.
This command can be used to insure the entire collection of atoms (or a subset of them) does not drift or rotate during the simulation due to random perturbations (e.g. fix langevin thermostatting).
Note that the velocity command can be used to create velocities with zero aggregate linear and/or angular momentum.
Restrictions: none
Related commands:
Default: none