On the Dynamics of Hydrogen‐Bonded Ferroelectrics

The dynamics of hydrogen‐bonded ferroelectrics described by the Ising spin system in a transversal field is investigated within the framework of the continued fraction method for correlation functions by Mori. The complete set of dynamical equations for the longitudinal and transversal relaxation functions derived in this paper is reduced in the high temperature limit to that obtained previously by Moore and Williams making use of the technique of Blume and Hubbard. It is shown that in this limit a short‐range Gaussian memory function related to the second‐order random force in the longitudinal relaxation function is a more appropriate choice than an exponential form which is equivalent to assume a three‐pole structure for this relaxation function. The critical behaviour near the transition point is briefly discussed.