Atomic and molecular correlation energies with explicitly correlated Gaussian geminals. IV. A simplified treatment of strong orthogonality in MBPT and coupled cluster calculations

Abstract

A simplified strong orthogonality projection has been introduced for the use in the many body perturbation theory (MBPT) or coupled cluster method (CCM) calculations with explicitly correlated geminals. This approximate projection efficiently eliminates the undesired strong orthogonality violating components from the perturbative or CCM pair functions. Moreover it permits dropping the exact strong orthogonality projectors from the pair equations. This results in a dramatic simplification of atomic and molecular calculations with explicitly correlated geminals.