First-Principles Calculations of Structural, Elastic, Electronic, and Optical Properties of Perovskite-type KMgH₃ Crystals: Novel Hydrogen Storage Material

Abstract

We report a first-principles study of structural and phase stability in three different structures of perovskite-types KMgH(3) according to H position. While electronic and optical properties were measured only for stable perovskite-type KMgH(3), our calculated structural parameters are found in good agreement with experiment and other theoretical results. We also study the electronic charge density space distribution contours in the (200), (101), and (100) crystallographic planes, which gives better insight picture of chemical bonding between K-H, K-Mg-H, and Mg-H. Moreover, we have calculated the electronic band structure dispersion, total, and partial density of electron states to study the band gap origin and the contribution of s-band of H, s and p-band of Mg in the valence band, and d-band of K in the conduction band. Furthermore, optical features such as dielectric functions, refractive indices, extinction coefficient, optical reflectivity, absorption coefficients, optical conductivities, and loss functions of stable KMgH(3) were calculated for photon energies up to 40 eV.

Recent Advances in Rare Earth‐Doped Hydrides

“…It is well‐known that the refractive index or changes of the refractive index of the host medium influence the radiative lifetime , . While the refractive index of metal hydrides is probably 2, the refractive index of many oxides with yellow Eu 2+ emission is rather approximately 1.6 . An increase of n from 1.6 to 2 is thus expected to more than double the radiative decay rate, which is in agreement with the observed decay rates in hydrides.…”

Crystal Structure and Luminescence Properties of the First Hydride Oxide Chloride with Divalent Europium: LiEu2HOCl2

“…The observation of shorter decay times than 1 μs can be explained by the presence of defects in these samples resulting in the promotion of a non‐radiative relaxation channel to the ground state, which shortens the lifetime of the excited state. Another explanation for a shorter lifetime could be a higher refractive index of about 2 for hydrides as compared to oxides or chlorides as already suggested as an explanation for the short lifetimes in pure hydrides by Kunkel et al…”

First principles study of alkali alkaline hydrides ABH3 (A = K, Rb, Cs and B = Mg, Ca)

“…Recently, Komiya et al [16] have reported the synthesis and decomposition of MMgH 3 (M = Na, K, Rb). The electronic structure, bonding and stability of typical perovskite-type hydrides MMgH 3 (M = Na, K, Rb) were theoretically investigated using first-principles methods [17][18][19][20][21][22]. CsCaH 3 is synthesized by Gingl et.al [23].…”