Many-Body Perturbation Theory and Coupled Cluster Theory for Electron Correlation in Molecules

Ten years ago in the Annual Review of Physical Chemistry. there was a review article entitled Many-Body Theories of the Electronic Structure of Atoms and Molecules, by Karl Freed ( 1 ) . In that article many-body methods were defined to be those techniques which derive their impetus from theories of the N-body problem for which N --+ 00. For the purposes of this review, we further specify these methods as many-body perturba­ tion theory (MBPT) (2-5) and the closely related coupled-cluster meth­ ods (CCM) (6-9) . In the ten years since that review appeared, probably no area in theo­ retical chemistry has undergone more development than has the theory, methodology, and applications of such ab initio many-body methods for