The use of the variational principle in molecular perturbation theory Available to Purchase

We have shown how the Variational Principle can be used to optimize the choice of the expansion functional and the reference state potential in molecular perturbation theory. The method was applied to a Stockmayer and to a Lennard‐Jones diatomic fluid. For the Stockmayer fluid, the variationally optimized expansion was identical to the Gray–Gubbins–Stell expansion that is based on choosing the potential as the expansion functional, and the unweighted mean of the full pair potentials as the reference state potential. For the Lennard‐Jones diatomic fluid, the variationally optimized expansion functional and reference state potential were intermediate between those of the Gray–Gubbins–Stell theory, and those of the reference average Mayer function (RAM) theory.