Mn-based hydride perovskites XMnH 3 (X = K, Li): A DFT study for physical properties, and hydrogen storage capability

The present study utilizes First-principles calculations to investigate the physical properties of Mn-based perovskite-type hydrides XMnH 3 (X = K, Li) including electronic, magnetic, and optical properties. The lattice parameters are calculated as 3.69 and 3.29 & Aring; for KMnH 3 and LiMnH 3 , respectively. The electronic and magnetic properties of both materials indicate that they are metallic and have ferromagnetic nature. The charge density, electron density and population analysis also have been analyzed to get an in-depth information about the structures of the studied materials. The reflectivity shows that both materials have a reflective surface due to the metallic nature. Both of the materials are found to be highly transparent and capable of accommodating polarization inside them. KMnH 3 is found to be more interactive with the incident photons and has a greater ability for polarization and storing the incident electromagnetic radiations. The optical conductivity described the conduction mechanism inside the materials. It is revealed that LiMnH 3 has a very low energy loss than KMnH 3 in the lower energy regime. Additionally, the hydrogen storage capability of Mn-based perovskite-type hydrides is briefly studied. The gravimetric hydrogen storage capacity is found to be 3.12 and 4.67 wt% for KMnH 3 and LiMnH 3 , respectively. The lower energy loss and higher gravimetric hydrogen storage capacity in LiMnH 3 suggest that it is a superior option for hydrogen storage applications.