Coexistence of ferroelectric and antiferroelectric microregions in the paraelectric phase of NH4H2PO4 (ADP)

J. LASAVE; S. KOVAL; R. L. MIGONI

Buenos Aires

Congreso; At the Frontiers of Condensed Matter IV, Tandar, BsAs; 2008

Abstract:Ammonium dihydrogen phosphate NH4H2PO4 (ADP) is an antiferroelectric (AFE) compound belonging to the KDP-type family of hydrogen-bonded ferroelectrics. Recent ab initio results have shown that the optimization of the N–H–O bridges in ADP leads to the stabilization of the AFE state over a FE one. However, electron spin probe measurements have suggested that microregions of both phases may coexist above the critical antiferroelectric–paraelectric transition temperature. We have performed first principles studies of the energetics and relative stability of different AFE and FE defects embedded in a paraelectric (PE) matrix of ADP. Our analysis indicates that FE and AFE clusters are stable and may coexist in the PE phase, thus confirming the above suggestion.