Numerical multiconfiguration self-consistent field study of the total (electronic and nuclear) parallel polarizability and hyperpolarizability for the OH, OH⁺, OH^-

Vibrational contributions to the molecular polarizability and hyperpolarizabilities are calculated for OH, OH⁺, and OH^- for an electric field directed along the bond axis. It was found that vibrational averaging of the polarizability works reasonably well for OH and OH^-, but fails for OH⁺, giving a result 16% to low. For the hyperpolarizabilities, the vibrational averaging strongly underestimates the vibronic contribution, whose size can exceed the electronic contribution, and therefore disqualifies this procedure for evaluation of these types of higher-order molecular properties.