A theoretical study of gas-phase basicities and proton affinities of alkali metal oxides and hydroxides

Abstract

B3LYP and PBE0 density functional calculations with different effective core potentials (ECP) and basis sets were used to investigate gas-phase geometries, basicities, and proton affinities of alkali metal oxides M 2O and hydroxides MOH (M=K, Rb, Cs). The alkali metal oxides and hydroxides were all found to be linear. We suggest the gas phase proton affinities for Rb 2O and Cs 2O to be 331.9 and 324.4 kcal/mol, respectively. Our calculations show that the most accurate method for calculating geometries of potassium, rubidium and cesium oxides and hydroxides is PBE0 density functional with CRENBL ECP and basis set (augmented with Glendening's polarization functions) on alkali metal, Dunning's double-zeta basis augmented with set of polarization and diffuse functions on oxygen, and Dunning's double-zeta plus polarization basis on hydrogen, while for proton affinities the B3LYP functional (with the same ECP/basis set combination) is marginally better.