Abstract
Detail analyzes to the electronic structure of magnesium based ternary metal hydrides containing alkali and alkaline-earth elements (α-CsMgH3) is reported so as to justify its use as advanced hydrogen storage systems. Calculations based on full-potential method within several exchange correlation potentials are performed to gain a reliable results. It has been found that α-CsMgH3 exhibits indirect band gap of about 2.3 eV (local density approximation -LDA), 2.6 eV (generalized gradient approximation -PBE-GGA), 2.9 eV (Engel-Vosko generalized gradient approximation - EVGGA) and 3.2 eV (recently modified Becke-Johnson potential -mBJ). The electronic band structure and the density of states reveal that at the energy regions around −5.0 eV and from −3.5 eV up to −2.0 eV the H-1s state hybridized with Mg-3s state to form a peak at around −5.0 eV and three peaks between −3.5 eV and −2.0 eV. The energy region from −2.0 eV up to Fermi level is originated by the interactions between H-1s and Mg-2p states. Thus, the interactions between the orbitals of H and Mg atoms leads to form strong covalent bonding between H and Mg atoms. The conduction bands are mainly originated from the empty states of Cs and partially from Mg-3s/2p states, while H-1s has insignificant contribution to the empty states. The chemical bonding were analyzed in term of charge density and charge transfer, we found that a charge transfer towards H atom occur. To gain further insight for deeply understanding the electronic structure, the optical dielectric functions are calculated based on the calculated band structure.
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