familiar temperature ranges. For a potential energy function E(p) relating to some geometric parameter p , we can use the chain rule to get the force on an atom at position (x,y,z) : (fx, fy, fz) = -E'(p) (∂p/∂x, ∂p/∂y, ∂p/∂z) where  ∂p/∂x  is the notation for the partial derivative of