Fifth-Order Many-Body Perturbation Theory and its Relationship to Various Coupled-Cluster Approaches

摘要

An analysis has been made of fifth order many body perturbation theory and its relationship to various coupled cluster approaches. The results show that the calculation of the fifth order energy is feasible and when carefully implemented may be applied to moderate sized systems. The number of terms that must be considered may be substantially reduced by taking into account the fact that many of the diagrams have identical values and many are amenable to factorization. (Reprints).