ABOUT THE INTRINSIC MECHANISMS OF THE CENTRAL PEAK PHENOMENON IN HYDROGEN-BONDED FERROELECTRICS

Using a Green's function technique a microscopic description of the in teraction constants delta(alpha) is given for three mechanisms of the formation of the central peak in K-bonded ferroelectrics: the relaxati onal mechanism, due to the coupling between the transverse soft-mode a nd the longitudinal mode; the oscillatory mechanism, caused by the cou pling between the transverse soft-mode and the phonon mode; the ''mixe d'' mechanism which could be treated as an effective coupling between the phonon and longitudinal modes. The dependence of delta(alpha) on t emperature and on the main parameters for H-bonded ferroelectrics is d iscussed.