Dynamical Susceptibility of Proton in a Two-Morse Potential

Abstract

Dynamical susceptibility for a proton tunneling system is investigated by using the linear response theory and the mean field approximation. The double-minimum self-potential is constructed by a two-Morse potential, whose parameters are fixed to represent O–H stretching mode. Quantum mechanical calculations give a dynamic susceptibility showing a pronounced soft mode. The phase transitions for KDP and DKDP are described qualitatively, if an effective interaction between protons and a phenomenological damping factor are introduced. The temperature dependence of the dynamical susceptibility is discussed.