Perovskite-type hydrides ACaH (A = Li, Na): computational investigation on materials properties for hydrogen storage applications.

Recently, perovskite materials have emerged as a multifunctional material for photovoltaics, luminescence, photocatalytics and hydrogen storage applications. This work reports a theoretical investigation on materials properties of hydride perovskite ACaH (A = Li, Na) with cubic phase of 3̄ space group for application of H storage material. Electronic structure calculations show that the cubic LiCaH and NaCaH have an indirect bandgaps of 2.1 and 2.3 eV with valence band maximum at point and conduction band minimum at point. Based on geometric factors, elastic constants and self-consistent phonon calculations, we reveal that ACaH can be dynamically stabilized in cubic phase at elevated temperatures, and the compounds are mechanically stable as well, satisfying Born's stability criteria. Finally, our calculations demonstrate that gravimetric (volumetric) H storage capacities are 5.99 and 4.54 wt% (63.77 and 60.93 g L), and dehydrogenation temperatures are 453.76 and 688.16 K with a consideration of quantum effect for A = Li and Na, respectively. This work highlights that cubic LiCaH is regarded as a potential H storage material due to its high H storage capacity, stability and suitable dehydrogenation temperature.