Atomic insights into the material properties of double-perovskite-type hydride LiNaMg<sub>2</sub>H<sub>6</sub> for H<sub>2</sub> storage applications.

Abstract

Perovskite-type compounds exhibit multi-functional properties that make them suitable for luminescence, photocatalysis, photovoltaics and H₂ storage applications. Here, we provide atomic insights into the material properties of the double-perovskite-type hydride LiNaMg₂H₆ for H₂ storage applications. Electronic structure calculations show that the cubic LiNaMg₂H₆ is an insulator with a direct band gap of 2.8 eV at the Γ point, consist with electron localization function and Born effective charge analyses. Based on geometric factors, elastic constants and self-consistent phonon calculations, we find that LiNaMg₂H₆ is dynamically and mechanically stable in the cubic phase at elevated temperatures, satisfying Born's stability criteria. Finally, it is illustrated that the gravimetric and volumetric H₂ storage capacities are 7.09 wt% and 91.12 g L^-1, and the H₂ desorption temperature is 548.54 K by considering the quantum effect, explaining well previous experimental observations. Our calculations highlight that LiNaMg₂H₆ hydride can be a potential H₂ storage material because of its high H₂ storage capacity, mechanical and dynamical stabilities and suitable H₂ desorption temperature.