Here is an interesting paper (or summary of an old Nato workshop course). It is by Shneior Lifson who sadly died in 2002. It was produced in 1981 and summarizes the details of potential energy functions, or forcefields, for the atomistic simulation of organic materials. Recommended reading for practitioners of the methods established by Lifson and his colleagues.
Potential Energy Functions for Structural Moleular Biology by Shneior Lifson, 1981