We now describe additive energy functions over a product space; here the product space is the conformational potential energy landscape of a molecule, with the number of terms in the product space determined by the degrees of freedom. We assume that the PEL V : X → R is a function over the product space X = X 1 × . . . × X n . Each space X i is equipped with a building block energy function g i : X i → R, and V is defined as V (x 1 , . . . ,