Abstract
The all-inorganic perovskite barium zirconate, BaZrO3, is a widely used material in a range of different technological applications. However, fundamental questions surrounding the crystal structure of BaZrO3, especially in regard to its ground-state structure, remain. While diffraction techniques indicate a cubic structure all the way down to T = 0 K, several first-principles phonon calculation studies based on density functional theory indicate an imaginary (unstable) phonon mode due to the appearance of an antiferrodistortive transition associated with rigid rotations of ZrO6 octahedra. The first-principles calculations are highly sensitive to the choice of exchange-correlation functional and, using six well-established functional approximations, we show that a correct description about the ground-state structure of BaZrO3 requires the use of hybrid functionals. The ground-state structure of BaZrO3 is found to be cubic, which is corroborated by experimental results obtained from neutron powder diffraction, inelastic neutron scattering, and neutron Compton scattering experiments.
Highlights
Perovskite-type oxides, of the general chemical formula ABO3, where A and B denote different metal ions, constitute an extremely important class of materials, with properties such as electronic and/or ionic conductivity,[1] multiferroicity,[2] piezoelectricity,[3] magnetocalorimetry,[4] and luminescence.[5]
The lack of superstructure and secondary phase peaks indicates that deviation from the BaZrO3 stoichiometry is accommodated by randomly distributed defects, which is consistent with the pronounced Lorentzian component of the peak shape
We have performed a study of the temperature dependence of the structure and dynamics of BaZrO3, using a multitechnique approach combining neutron powder diffraction, inelastic neutron scattering, neutron Compton scattering, and firstprinciples density functional theory calculations
Summary
Perovskite-type oxides, of the general chemical formula ABO3, where A and B denote different metal ions, constitute an extremely important class of materials, with properties such as electronic and/or ionic conductivity,[1] multiferroicity,[2] piezoelectricity,[3] magnetocalorimetry,[4] and luminescence.[5]. BaZrO3, with a nearly optimal tolerance factor of t = 1.0117 is a prominent candidate perovskite to stay cubic down to T = 0 K Both X-ray and neutron powder diffraction (XRPD and NPD, respectively) data, suggest a cubic structure down to, at least, T = 2 K.20. Recent Raman studies on a single-crystal sample of BaZrO3 show no direct evidence for such “nanodomains”, and the spectra are instead explained by classical second-order Raman scattering.[31] as our knowledge about the real ground-state structure of BaZrO3 has advanced, it has become clear that this seemingly simple material is a very challenging one It is only through a more systematic, combined experimental and theoretical study that a clear mechanistic picture of the ground-state structure of. Six different wellestablished XC functional approximations are used in the DFT calculations to carefully investigate the accuracy of the theoretical predictions and, together with the experimental studies, establish the structure of BaZrO3
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