Ab initio study of the low-lying electronic states of Ag3−, Ag3, and Ag3+: A coupled-cluster approach

Abstract

The low-lying electronic states of Ag3−(1Σg+,3B2), Ag3(2B2,2A1,2B1,4B2,2Σu+,1 2Σg+,2 2Σg+,2Πu,4Σu+), and Ag3+(1A1,1Σg+,3Σu+,3A1) are studied by ab initio calculations with the Stuttgart effective core potentials and corresponding (8s7p6d)/[6s5p3d] and (8s7p5d3f )/[6s5p3d3f] basis sets. The geometries, vibrational frequencies, and energetic splittings are obtained by the coupled-cluster method including singles and doubles (CCSD) and those including up to the noniterative triples [CCSD(T)] correlation methods with additional frozen core molecular orbitals corresponding to 4s and 4p orbitals. The results for well-studied states (Ag3− 1Σg+;Ag3 2B2,2A1,2Σu+;Ag3+ 1A1) are in good agreement with previous experimental results, and therefore our results for other newly studied states are expected to be reliable. The vertical detachment energies of Ag3− are obtained by the electron excitation equation-of-motion coupled-cluster (EE-EOM-CCSD) method and the average deviation from the experimental results is small without any scaling correction of the obtained values. The effect of the f-functions in the basis sets and the noniterative triples in the CCSD(T) method is discussed; the bond lengths are reduced significantly and the vertical detachment energies and ionization potentials are in much better agreement with experiment.