Using first-principles calculations, an investigation was made of the properties of (A,)Nb2O6 perovskite systems with a rocksalt ordering between divalent A atoms (Ca, Sr, Pb or Ba) and neutral vacancies, . Their properties could be understood by simple rules and by analogy with the corresponding ATiO3 simple perovskites. Contrary to common belief, all the studied vacancy-rich systems exhibited ferroelectric instability. Furthermore, their ground state could be ferroelectric, antiferrodistortive, and may be sensitive to pressure or quantum effects, depending upon the A atom.

Properties of Vacancy-Rich Ordered (A,[ ])Nb2O6 Perovskites. H.Crogman, L.Bellaiche: Physical Review B, 2002, 66[22], 220103 (4pp)