New Developments in Many Body Perturbation Theory and Coupled Cluster Theory

Abstract

Many body perturbation theory (MBPT) methods using the Moller-Plesset (MP) perturbation operator [1] are the most popular correlation corrected ab initio methods in Quantum Chemistry for calculating dynamic electron correlation effects. [2-9] The popularity of MP methods results from several reasons: (a) MP theory leads to a hierarchy of well-defined methods, which provide increasing accuracy with increasing order n. (b) Correlation effects are included stepwise in a systematic manner that facilitates their analysis and the understanding of the correlation problem. (c) Most important is the fact that all MP methods are size-extensive. [3,10] (d) Up to fourth order, MP energies can be calculated at relatively small computational cost since calculations involve just single, noniterative evaluation steps.