Novel MgBH3 (B = Al, Si, P, S) perovskites Predicted via DFT for high-performance solid hydrogen systems

Global warming and the exhaustion of non-renewable energy resources are two significant concerns confronting the contemporary world. Researchers are increasingly concentrating on clean energy carriers to address these challenges, with hydrogen emerging as a viable alternative owing to its non-polluting characteristics. Nonetheless, efficient hydrogen storage continues to pose a significant scientific problem. Perovskite hydrides are distinguished among promising materials for their elevated gravimetric hydrogen capacity and ion exchangeability. This work examined the structural, mechanical, thermodynamic, electronic, optical, and hydrogen storage properties of MgBH₃ (B = Al, Si, P, and S) compounds utilizing density functional theory (DFT) through the Cambridge Serial Total Energy Package (CASTEP). The lattice constants for MgAlH₃, MgSiH₃, MgPH₃, and MgSH₃ were determined to be 3.769, 3.711, 3.609, and 3.709 Å, respectively. All hydrides demonstrated mechanical stability except MgPH₃ according to Born's stability requirements. MgAlH₃ is stiffer than other materials, as evidenced by bulk, shear, and Young's modulus. Each material is naturally anisotropic, corresponding to the anisotropy factor A. All materials exhibit a ductile nature, corresponding to Poisson's ratio. In the same way, according to Pugh's ratio, MgAlH₃ exhibits a ductile nature and all other material's brittle nature. Cauchy's values for each material are positive, explaining their metallic bonding and ductile nature. Analysis of the electronic structure indicated metallic behaviour resulting from the overlap of the conduction band minimum and the valence band maximum. Negative formation energies confirmed thermodynamic stability. Phonon dispersion analysis confirms the dynamical stability of MgBH₃ (B = Al, Si, P, and S) compounds. Thermodynamic parameters like Debye temperature against temperature and elevated melting temperature for MgBH₃ (B = Al, Si, P, and S) compounds reveal the stability and appealing characteristics for utilization in hydrogen storage. The optical properties were analyzed, revealing that the materials demonstrate adequate absorption in the low-energy spectrum, advantageous for hydrogen storage applications. The hydrogen storage capacities were 5.27 %, 5.17 %, 4.93 %, and 4.8 % for MgAlH₃, MgSiH₃, MgPH₃ and MgSH₃, respectively. These findings underscore the promise of MgBH₃ (B = Al, Si, P, and S) perovskites for effective hydrogen storage applications in forthcoming energy systems.