I structured (dopped) a metal onto the Graphene sheet. It is a 2D single-layer structure. When I go to optimize and calculate some properties of it, the layer always slides from the vacuum slab! Is it normal? or did I make a mistake somewhere? In the calculation, I put all the requests below:

Setup: See the attachment please.

May I get a guide from anybody? An advance thanks from me. 

Keshab K. Adhikary