The temperature and pressure dependence of the proton tunnelling frequency in KDP

Abstract
A double-minimum potential, constructed by placing two Morse functions back to back, is used to calculate the single-particle proton energy levels in KDP. The potential well parameters are estimated from infrared and crystallographic data. The temperature and pressure dependence of the proton tunnelling frequency is computed. The soft-mode Raman scattering data of Percy (1973) are re-analysed, allowing for the temperature dependence of the tunnelling frequency and for its modulation by the oxygen-oxygen thermal motion.