you need to set the force for y and z as zero also. velocity set just set the begining velocity.
Hi Zhang Junjie and All:
The picture looks weird to me as the tip looks perfectly intact, i.e.
was not deformed at all. Why?
I think you might want to increase the masses of the Atoms of type 4.
That would reflect the fact that the tip is macroscopic.
Z. Insepov