State-specific coupled cluster-type dressing of multireference singles and doubles configuration interaction matrix

Using the theory of state-specific self-consistent intermediate Hamiltonians, one proposes a new dressing of a multireference (MR) singles and doubles configuration interaction (CI) Hamiltonian matrix which insures size consistency. The method is based on a coupled cluster (CC) type factorization of the coefficients of the triples and quadruples and can be considered as leading to a dressed CI formulation of a state-specific MRCC method. Preliminary application of the new procedure to the H4 model and comparison with other MRCC schemes are presented.