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a b s t r a c tThe structural and vibrational properties of SrHfO 3 compared to those of the SrZrO 3 were investigated using first-principles calculations. The phonon dispersion curves, reported in the high-symmetry cubic perovskite phase, point out the coexistence of structural antiferrodistortive instabilities at the R and M zone-boundary points and a ferroelectric instability at the zone center. Different possible intermediate phases are characterized by comparing their internal energies, giving the same hierarchy of phases as for the SrZrO 3 . The main features of the ferroelectric instability are also discussed, and, contrary to what was found for SrZrO 3 , it seems very unlikely to induce the ferroelectricity in the SrHfO 3 Pnma ground state either by compressive or tensile epitaxial strain.

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Using first-principles calculations, we investigate the structural and vibrational properties of PbZrO 3 . Starting from the high-symmetry cubic perovskite phase, for which the phonon dispersion curves are reported to have many unstable branches, we identify some key intrinsic characteristics allowing the prediction of materials with the propensity of developing an antiferroelectric behavior. We confirm the key role that R antiferrodistortive modes play in condensing the observed antiferroelectric phase, via a cooperative bilinear coupling, and the nearest with the ferroelectric state. Our work shows that, given all their important potential wells none of the individual modes condensed deletes all other and that it is their coupling which plays a key role in the condensation of the ground state lead zirconate, and these couplings would explain why Pbam and R3c phases are close in energy for promoting the first order transition.