Partition function intermolecular-potential-based

Fickett in "Detonation Properties of Condensed Explosives Calculated with an Equation of State Based on Intermolecular Potentials , Los Alamos Scientific Lab Rept LA-2712 (1962), pp 34-38, discusses perturbation theories as applied to a system of deton products consisting of two phases one, solid carbon in some form, and the other, a fluid mixt of the remaining product species. He divides these theories into two classes conformal solution theory, and what he chooses to call n-fluid theory. Both theories stem from a common approach, namely, perturbation from a pure fluid whose props are assumed known. They differ mainly in the choice of expansion variables. The conformal solution method begins with the assumption that all of the intermolecular interaction potentials have the same functional form. To obtain the equation of state of the mixt, some reference fluid obeying a common reduced equation of state is chosen, and the mixt partition function is expanded about that of the reference fluid... 

Other potential functions differ in the way the potential is partitioned into various contributions representing intra and intermolecular interactions. Cornell and collaborators 300 proposed an approach to determine the force field parameters based as much as possible on ab initio calculations. In this work each biomolecular system is divided into small residua, for which geometry optimization can be performed by an ab initio method. Ab initio calculations give partial atomic charges on atoms and the equilibrium geometry, i.e. the equilibrium values for the bond lengths, and planar and dihedral angles. 

---