Understanding the ferroelectric phase transition in H-bonded materials by ab initio calculations: the case of KH2PO4 (KDP) and KD2PO4 (DKDP)

G. COLIZZI; J. KOHANOFF; S. KOVAL; R. MIGONI

Cambridge

Conferencia; X European Meeting on Ferroelectricity 2003; 2003

Abstract:Results of first-principles calculations are reported for KDP and DKDP as a function of pressure. The global energy barrier between the two stable (oppositely polarized) equilibrium configurations, and the separation between the corresponding positions of the H-atoms in the O─H─O bridges, are analyzed in terms of a previously proposed, self-consistent double-well model. We argue that the experimentally observed similarity of the H(D) off-centering distance in KDP and DKDP at the transition temperature can be explained only by means of important geometric isotope effects.