Treatment of core-valence correlation effects through difference-dedicated configuration interaction: Application to the lowest electronic states of K, Rb, KH, RbH, and K2

The iterative difference dedicated configuration interaction (IDDCI) method, recently proposed for calculating excited electronic states, is tested in systems where the core-valence correlation plays an important role. The calculated ionization potential, electron affinity, and electronic transition energies of K and Rb agree within 0.1 eV with experimental values. The three lowest Σ+ potential curves of KH and RbH and the six lowest states Σg+, Σu+, and Πu of K2 are calculated with the same accuracy.