THE ROLE OF LATTICE SYSTEM ON FERROELECTRIC PHASE-TRANSITION IN PBHPO4

In view of the importance of the role of host lattice on the proton co nfigurations in hydrogen-bonded crystals, a cluster theory is develope d to explain the phase transition in one-dimensional ferroelectrics Pb HPO4. The correlation between the spontaneous polarization and Pb-PO4 translational mode frequency is analyzed on the basis of a pseudo-spin model for the proton system. It is shown that rather high transition temperature T(c) in this system is related with the large anisotropy a mong proton-proton correlations and the renormalization of the host la ttice into proton system.