Note on Isotope Effect in Hydrogen Bonded Crystals

Abstract

By making use of a simple model potential for hydrogen bond, empirical relation between oxygen-oxygen distance and oxygen-hydrogen distance found widely in various hydrogen bonded crystals is explained. It is pointed out that, between theoretical prediction and observed empirical data, there exists a salient discrepancy which is to be resolved by considering quantum effect or tunneling motion of hydrogen atom. The tunneling effect is treated by a variational method on a one dimensional model of hydrogen bond. Possibility of isotope effect in hydrogen bond length is examined and some speculation is given on a new interpretation of the isotope effect in ferro or antiferroelectric phase transition temperatures in hydrogen bonded crystals. 1.