Proton mobility in metallic copper hydride from high-pressure nuclear magnetic resonance

Abstract

The atomic and electronic structures of ${\mathrm{Cu}}_{2}\mathrm{H}$ and CuH have been investigated by high-pressure nuclear magnetic resonance spectroscopy up to 96 GPa, X-ray diffraction up to 160 GPa, and density functional theory-based calculations. Metallic ${\mathrm{Cu}}_{2}\mathrm{H}$ was synthesized at a pressure of 40 GPa, and semimetallic CuH at 90 GPa, found stable up to 160 GPa. For ${\mathrm{Cu}}_{2}\mathrm{H}$, experiments and computations show an anomalous increase in the electronic density of state at the Fermi level for the hydrogen $1s$ states and the formation of a hydrogen network in the pressure range 43--58 GPa, together with high $^{1}\mathrm{H}$ mobility of $\ensuremath{\sim}{10}^{\ensuremath{-}7}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{2}/\mathrm{s}$. A comparison of these observations with results on FeH suggests that they could be common features in metal hydrides.