Pressure-Stabilized Cubic Perovskite Oxyhydride BaScO2H

Abstract

We report a scandium oxyhydride BaScO₂H prepared by solid state reaction under high pressure. Rietveld refinements against powder synchrotron X-ray and neutron diffraction data revealed that BaScO₂H adopts the ideal cubic perovskite structure (Pm3̅m), where oxide (O^2-) and hydride (H^-) anions are disordered. ¹H nuclear magnetic resonance (NMR) spectroscopy provides a positive chemical shift of about +4.4 ppm, which can be understood by the distance to the nearest (and possibly the next nearest) cation from the H nucleus. A further analysis of the NMR data and calculations based on ab initio random structure searches suggest a partial cis preference in ScO₄H₂ octahedra. The present oxyhydride, if compositionally or structurally tuned, may become a candidate for H^- conductors.