A b i n i t i o study of the alkali and alkaline-earth monohydroxides

The structure and energetics of the alkali and alkaline-earth monohydroxides are studied at both the self-consistent-field and singles plus doubles configuration-interaction level using Gaussian basis sets of at least triple-zeta plus double polarization quality. BeOH is found to be bent, with a very flat bending potential. MgOH is found to be linear, and all remaining alkali and alkaline-earth hydroxides are known to be linear. Our recommended dissociation energies, D0, in eV are LiOH (4.64), NaOH (3.51), KOH (3.61), RbOH (3.58), CsOH (3.78), BeOH (4.70), MgOH (3.31), CaOH (4.15), SrOH (4.19), and BaOH (4.6). The dissociation energies are estimated to be accurate to 0.10 eV, except for BaOH where the estimated uncertainty is at least 0.2 eV owing to the use of a relativistic effective core potential. The theoretical dissociation energies are shown to have a strong correlation with those of the corresponding fluorides and oxides.