Fock space multireference coupled cluster method with full inclusion of connected triples for excitation energies

We report the initial Fock space multireference coupled cluster method with the full inclusion of single, double, and triple excitations (FS-CCSDT) for the (l,l) sector. We present pilot applications for calculating excitation energies for the N-2 molecule and the Ne atom. The performance of the current model, along with the FS-CCSD one, has been studied in comparison with the equation-of-motion coupled-cluster and the similarity transformed methods. (C) 2004 American Institute of Physics.