Hydrogen storage is an urgent issue for mobile applications, to overcome this issue solid materials have a potential role for hydrogen storage applications. Moreover, the perovskite hydride materials have been extensively investigated for improvement in the field of hydrogen storage. However, this work is focused on the computational study of XAlH (X: Na, Mg) perovskite-type hydrides for different physical properties and hydrogen storage applications. Both materials were found thermodynamically, and mechanically stable from the negative formation energy and elastic properties. They exhibited cubic phases with computed lattice constants are 3.827 Å and 3.752 Å, respectively. The electronic properties indicated that both compounds have a metallic nature, and found the high contribution of Al-p state, and H-1s state near the Fermi level. However, the Hirshfeld net charge analysis detected, that charge transfer from Al and X (Na, Mg) atoms to H atoms. Furthermore, the metallic hydrides have promised candidates for hydrogen storage applications. Both compounds have observed non-magnetic behavior with zero magnetic moments. Elastic constants were calculated to determine the mechanical stability of the compounds, it was found that MgAlH is harder than NaAlH, and it exhibited that higher Bulk, Shear, and Young's modulus. The Poisson's, and Pugh's (G/B) ratios suggested that ionic boning of the atoms, additionally, Pugh's ratio (B/G) and Cauchy pressure (C) confirmed that NaAlH ductile and MgAlH is brittle behavior. Besides this, Optical properties were determined for both compounds including the dielectric function, conductivity, refractive index, absorption, and loss function. It is found that the MgAlH compound optical more suitable than NaAlH due to calculated optical factors promised and both compounds are undertaken for solar cells, optoelectronics, and energy storage applications. Finally, the computed hydrogen storage capacity for NaAlH and MgAlH compounds are 6.01 wt%, and 5.56 wt% respectively. These results revealed that both have the potential materials for hydrogen storage, but NaAlH unique material to fulfill the US-DOE criteria of 2020.

中文翻译：

---

铝基氢化物储氢应用的基本原理见解

储氢是移动应用的一个紧迫问题，克服这一问题的固体材料对于储氢应用具有潜在的作用。此外，钙钛矿氢化物材料已被广泛研究以改善储氢领域。然而，这项工作的重点是针对不同物理性质和储氢应用的 XAlH（X：Na，Mg）钙钛矿型氢化物的计算研究。这两种材料都具有热力学稳定性，并且由于负形成能和弹性特性而具有机械稳定性。它们表现出立方相，计算出的晶格常数分别为 3.827 Å 和 3.752 Å。电子性质表明两种化合物均具有金属性质，并发现费米能级附近的Al-p态和H-1s态贡献较高。然而，赫什菲尔德净电荷分析发现，电荷从 Al 和 X（Na、Mg）原子转移到 H 原子。此外，金属氢化物有望成为储氢应用的候选者。两种化合物都观察到零磁矩的非磁性行为。计算弹性常数以确定化合物的机械稳定性，发现MgAlH比NaAlH更硬，并且表现出更高的体积模量、剪切模量和杨氏模量。泊松比 (G/B) 和普格 (G/B) 比表明原子的离子键合，此外，普格比 (B/G) 和柯西压力 (C) 证实 NaAlH 具有延展性，而 MgAlH 具有脆性行为。除此之外，还确定了两种化合物的光学性质，包括介电函数、电导率、折射率、吸收和损耗函数。研究发现，由于计算出的光学系数，MgAlH 化合物比 NaAlH 更适合光学，并且这两种化合物都可用于太阳能电池、光电子和储能应用。最后，计算得出 NaAlH 和 MgAlH 化合物的储氢容量分别为 6.01 wt% 和 5.56 wt%。这些结果表明，两者都具有潜在的储氢材料，但 NaAlH 是满足美国能源部 2020 年标准的独特材料。