atom stress and adhesive force

Hello everyone,
Now I am using the lammps to simulate the zinc oxide and graphene. I want to calculate the adhesive force between them when graphene was separated gradually form zinc oxide. But I can only get the stress of graphene by using compute command. Can anyone tell me how to transfer the stress to adhesive force? Thank you so much!

Wow, your advisor (?) just asked a very similar question. Maybe you
should meet with him/her.

Adhesive force between two slabs is just the sum of the forces when
these two slabs are together forming an interface minus the forces
whey they are separated.

Ray