Conceptual design and stand-alone multiscale simulation for hydrogen storage energy: A rigorous way forward for double hydride perovskites Na2YH6 (Y = Ca, Ti)

We investigated sodium based double hydrides Na 2 YH 6 (Y = Ca, Ti) using first principles calculations. The structural, mechanical, thermodynamic and optoelectronic properties are calculated for complete theoretical analysis. The structural properties are evaluated by the optimized lattice constant and bulk modulus. The negative formation energies not only confirm the stability but also the reaction pathways through convex hull analysis. The gravimetric hydrogen storage capacity of Na 2 CaH 6 and Na 2 TiH 6 is 6.17 wt% and 5.72 wt% respectively. The different mechanical parameters highlighted the greater mechanical strength of Na 2 TiH 6 than Na 2 CaH 6 . The band curves indicating the metallic nature of Na 2 CaH 6 and semiconducting nature of Na 2 TiH 6 with band gap of 0.921 eV. The complex dielectric function, refractive index and reflectivity are also calculated for both hydrides. The effect of applied pressure and temperature is investigated on thermodynamic parameters. The high gravimetric hydrogen storage capacity advocates the greater potential of these hydrides for hydrogen storage applications.