MULTIREFERENCE SELF-CONSISTENT SIZE-CONSISTENT SINGLES AND DOUBLES CONFIGURATION-INTERACTION FOR GROUND AND EXCITED-STATES

One proposes a state-specific self-consistent dressing of the configur ation interaction (CI) matrix built on a multireference space and all the singly and doubly substituted determinants. The dressing insures s ize consistency [and separability when localized molecular orbitals (M Os) are used]. In the here-proposed solution, which generalizes a prev ious single reference method [(SC)(CI)-C-2, J. Chem. Phys. 99, 1240 (1 993)] valid only for the research of the ground state, all the referen ce determinants play an equal role and the method is applicable to exc ited states. The implementation will be simpler if the reference space is a complete active space, but this restriction is not compulsory.