Two-dimensional vibrational analysis of the Lippincott-Schröder potential for OHO, NHO and NHN hydrogen bonds and the deuterium isotope effect

Abstract

Two-dimensional vibrational analyses [i.e. crude adiabatic approximation, SCF approximation and variational method (crude adiabatic basis function)] are performed on the hydrogen bond systems consisting of the Lippincott-Schröder potentials for the OHO, NHO and NHN bonds. The OHO and NHN systems are supposed to be linear and the bent structure is considered for the NHO system. The frequency shift for the hydrogen bond length variation and its deuterium substitution effects are in good agreement with experiment. The anomalies in the frequency ratio ν OH/ν OD at an O—O distance of 2.5 Å, and in the interminimum distance shift on deuteration at 2.5 Å are well explained as the difference of double minimum behavior between the vibrational states of proton and deuterium. It is also shown that the Lippincott-Schröder model for the OHO system supplies the general features for proton tunneling, proton delocalization beyond the barrier and other type processes in hydrogen bonds.