Theory of Phase Transitions in Mixed Crystals Rb1-x(NH4)xH2PO4

Abstract

Within the cluster approximation, phase transitions in the mixed crystals of hydrogen bonded ferroelectrics and antiferroelectrics Rb1−x(NH4)xH2PO4 are discussed on the basis of a pseudospin model for the proton system. The phase diagram of this system in the temperature-composition plane is derived theoretically and compared with the experimental results in good agreement.