Relaxation dynamics of deuterated ferroelectric orthophosphates

Dynamical model of the deuterated ferroelectric orthophosphates is suggested. Taking into account the short- and long-range interaction in the cluster approximation, the system of equations for the deuteron distribution functions depending on time is obtained. The deuteron distribution functions in the case of small deviations from the equilibrium state and comparatively large temperature interval in the phase transition region are found. On the basis of the results obtained the relaxation phenomena in the ferroelectrics of the KD$_2$P0$_4$ type are considered.