Selective Hydride Occupation in BaVO3–xHx (0.3 ≤ x ≤ 0.8) with Face- and Corner-Shared Octahedra

A growing number of transition metal oxyhydrides have recently been reported, but they are all confined to perovskite-related structures with corner-shared octahedra. Using high pressure synthesis, we have obtained vanadium oxyhydrides BaVO3–xHx (0.3 ≤ x ≤ 0.8) with a 6H-type hexagonal layer structure consisting of face-shared as well as corner-shared octahedra. Synchrotron X-ray and neutron diffraction measurements revealed that, in BaVO2.7H0.3, H– anions are located selectively at the face-shared sites, as supported by DFT calculations, while BaVO2.2H0.8 contains H– anions at both sites though the face-shared preference is partially retained. The selective hydride occupation for BaVO2.7H0.3 appears to suppress electron hopping along the c axis, making this material a quasi-two-dimensional metal characterized by anomalous temperature dependence of the electrical resistivity and strong antiferromagnetic fluctuations. In contrast, the anion disordered BaVO3–xHx in hexagonal (x ≈ 0.8) and cubic (x ≈ 0.9) fo...