The fourth order diagrammatic MB-RSPT calculations of the correlation energy of ten electron systems

The aim of this work is to analyze the correlation energy of the 10-electron systems Ne, HF, H2O, and NH3, using the diagrammatic many-body perturbation theory up to the fourth order. The second and third order contributions are included fully. In the fourth order, attention was directed to the detailed analysis of the inter-relation of contributions which arise from all double excitations, from the renormalization term as well as from quadruple excitations which are due to non-EPV contributions from quadruple excitations diagrams. The connections with other methods are also discussed.