Four-and 8-Reference State-Specific Brillouin-Wigner Coupled-Cluster Method: Study of the Singlet Oxygen

摘要

We developed and implemented the state-specific Brillouin-Wigner coupled-cluster theory restricted to single to single and double excitations (BWCCSD) method for a general number of closed-and open-shell reference configurations. The method (together with the previously suggested a posteriori size-extensivity correction) is applied to the calculation of oxygen molecule in the X~3SUM_g~-, a~1DELTA_g, and b~1SUM_g~+ states, and results of this multireference treatment are compared with those obtained by the DIP STEOMCCSD and multireference (MR)-CISD methods and with experimental spectroscopic data.