Application of Dyson-corrected second-order perturbation theories

Previously [Y. Mochizuki, Chem. Phys. Lett. 453 (2008) 109], the self-energy shift obtained from the Dyson equation was introduced to modify the energy denominator of the second-order perturbational estimate for orbital relaxations in the method of configuration interaction singles with perturbative doubles, CIS(D). This Dyson correction technique is then applied also to the differential second-order correlation energy in CIS(D) calculations, in conjunction with the partial renormalization (PR) of amplitudes by using the topological factor. The potential of Dyson/PR-corrected second-order perturbation itself is separately examined with a couple of small systems having elongated bonds at the ground state.