Application of the intermediate Hamiltonian valence-universal coupled-cluster method to atomic systems with one valence electron

The atomic version of valence-universal coupled-clusters method in the intermediate Hamiltonian formulation with one- and two-body part included in the cluster operator is applied to describe the ground state and some excited states of Li, B, Na, and Mg+ atomic systems. The Slater-type spdfg basis sets are employed. The results are corrected for the three-body cluster operator which is included in an approximate way into the method as a noniterative correction of the third order in the perturbation. Values of calculated ionization potentials and excitation energies are well reproduced, however, the effects of three-body clusters are, with an exception for the B atom, small for the considered systems.