Ni-induced photoabsorption and hydrogen desorption on the Li–Mg hydrides using ab initio calculation

Abstract

Electronic effects of Ni dopant into the host Li–Mg hydrides as the compositions of 16LiMgH3 and 12Li2MgH4 are investigated using an ab initio investigation. Based on the basic concepts of density functional theory, all structures are optimized and calculated electronic properties using the Perdew-Burke-Ernzerhof functional scheme. In a supercell method, the Ni dopant is substituted on the Mg site in the supercell due to the equal oxidation numbers. It is found that Ni dopant reduces the volume cell size and band gap of the host-hydride supercells. The Ni-doped system exhibits a better absorption for a high coefficient in the visible light region. To determine the ability of the hydrogen removal from the LiMgH3 and Li2MgH4 systems, the Ni-doped systems present the lower H-vacancy formation energy, indicating an easier release of hydrogen from the host Li–Mg hydrides.