Chapter 8, Problem 27P

The potential energy function for either one of the two atoms in a diatomic molecule is often approximated by $U(x)=-a/x^{12}-b/x^6$ where x is the distance between the atoms. (a) At what distance of separation does the potential energy have a local minimum $\left(x=\infty \right)$ ? What is the force on an atom at this separation? (c) How does the force vary with the separation distance?