Move a cluster

Hello dear lammps user,
i have a question about moving a silicon cluster in the Z direction.
the sphere cluster is located on the top of a nanosheet.

in the location of the cluster, i defined a group :

region cluster block 40 60 40 60 40 60 units box
group cluster region cluster

then i used this commands to move the cluster in z direction:

velocity group-id set vx vy vz unit force

velocity cluster set 0.0 0.0 ${LR} units box

fix id group-id setforce fx fy fz

fix 005 cluster setforce 0.0 0.0 NULL

where LR is the value of the velocity

But it didnt move at all. then i tried to do this with fix move command.

fix clusterMoving cluster move linear NULL NULL -${LR} units box

but it still doesn’t move. May i ask what is the problem? Thank you very much

Kind regards,


Please provide more detail about your input file. For example, how much is LR?!