Structural, Electronic, and Hydriding Properties of Li$_{2}$MgSi

An investigation of Li$_{2}$MgSi, with particular emphasis on its potential as a hydrogen storage material, is reported. A cubic P$\overline{4}$3m crystal structure, differing from previous determinations, is established. We find that the material reversibly sorbs $\sim $2.8 mass{\%} hydrogen at T $\sim $ 300\r{ }C according to the reaction Li$_{2}$MgSi + H$_{2}$ $\leftrightarrow \quad \raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} $Mg$_{2}$Si + 2LiH + $\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} $Si. Electronic structure calculations indicate that Li$_{2}$MgSi is a semiconductor with a small, indirect gap of $\sim $0.2 eV.