Syntax:
fix ID group-ID setforce fx fy fz
Examples:
fix freeze indenter setforce 0.0 0.0 0.0 fix 2 edge setforce NULL 0.0 0.0
Description:
Set each component of force on each atom in the group to the specified values fx,fy,fz. This erases all previously computed forces on the atom, though additional fixes could add new forces. This command can be used to freeze certain atoms in the simulation by zeroing their force, assuming their initial velocity zero.
Any of the fx,fy,fz values can be specified as NULL which means do not alter the force component in that dimension.
The forces due to this fix are also imposed during an energy minimization, invoked by the minimize command.
The total force on the group of atoms before it is reset is stored by the fix and its components can be accessed during thermodynamic print-out by using f_ID[N] where ID = he fix-ID and N = 1,2,3. See the thermo_style custom command for details. Note that the fix stores the total force on the group of atoms, but the printed value may be normalized by the total number of atoms in the simulation depending on the thermo_modify norm option you are using.
Restrictions: none
Related commands:
Default: none