One trillion atoms of the heaviest element is less than a nanogram. I get your point it's just that we can't even simulate all the blades of grass on a one acre lawn with every shortcut we have.

Really I think it would be cool to explore -- I've been working on a procedural game engine (conceptually at least) for a long time and want to incorporate even "basic" things like chemistry. I think it's still decades away for that, not even considering quantum phenomena.