The role of π-blocking hydride ligands in a pressure-induced insulator-to-metal phase transition in SrVOH.

Transition-metal oxyhydrides are of considerable current interest due to the unique features of the hydride anion, most notably the absence of valence p orbitals. This feature distinguishes hydrides from all other anions, and gives rise to unprecedented properties in this new class of materials. Here we show via a high-pressure study of anion-ordered strontium vanadium oxyhydride SrVOH that H is extraordinarily compressible, and that pressure drives a transition from a Mott insulator to a metal at ~ 50 GPa.