New Partitioning Perturbation Theory. III. Applications to Electron Exchange

A new partitioning perturbation technique provides a rigorous derivation and generalization of the Hirschfelder–Silbey formalism for treating electron exchange problems. A new method of solving the first-order perturbation equation is introduced. The first-order wavefunction is the sum of the polarization function which describes van der Waals correlations and an exchange function which introduces ionic terms. The exchange function is determined variationally for both the ground-state H+H+ and H+H interactions. In the many-electron case, the first-order equation reduces to a set of one- and two-electron equations.