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fix setforce command

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.

Restart, fix_modify, thermo 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.

The total vector force on the group of atoms before it is reset is stored by the fix and its components can be printed as part of thermodynamic output via the keywords f_ID[N] where ID is the fix-ID of this fix 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 being used.

No parameter of this fix can be used with the start/stop keywords of the run command.

The forces due to this fix are imposed during an energy minimization, invoked by the minimize command.

Restrictions: none

Related commands:

fix addforce, fix aveforce

Default: none