Pressure-Induced Transitions in the 1-Dimensional Vanadium Oxyhydrides SrVOH and SrVOH, and Comparison to 2-Dimensional SrVOH.

High-pressure X-ray diffraction measurements on the layered oxyhydrides SrVOH and SrVOH reveal that both compounds undergo a pressure-induced rock-salt to CsCl (1-2) structural transition, similar to those observed in binary compounds (oxides, halides, chalcogenides, etc.). This structural transition, observed at 43 and 45 GPa in SrVOH and SrVOH, respectively, relieves almost all of the accumulated strain on the infinite V-O-V ladders, such that the V-O bond lengths are almost identical at 0 and 50 GPa but are substantially compressed at intermediate pressures. The resistances of both materials with 1-dimensional VO ladders decrease with increasing pressure, but unlike SrVOH that contains 2-dimensional VO sheets, they remain insulating even at the highest accessible pressures. The reduction in dimensionality from planar to linear VO networks reduces the dispersion of the V-O π bands that define the band gap and leads to insulating behavior at all measured pressures.