I am attempting to develop some code that uses an external quantum mechanical calculation to determine the forces acting on the atoms. I need to calculate the box pressure but I'm not sure how to go about doing that if all I have is the forces acting on each atom. I know if I had pair interactions, I could use the Virial pressure but I don't have those. Can someone give me a little information on how pressure is calculated or a few references/keywords so I can figure this out?
Thanks for the help.