State-of-the-art electronic structure calculations yield results consistent with the observed compound SiLi2Mg and provide likelihood of the availability of IrLi2Mg and RhLi2Mg. Similar calculations provide likelihood of the availability of YLi2MgHn, ZrLi2MgHn, NbLi2MgHn, MoLi2MgHn, TcLi2MgHn, RuLi2MgHn, RhLi2MgHn, LaLi2MgHn, Ce4+Li2MgHn, Ce3+Li2MgHn, PrLi2MgHn, NdLi2MgHn, PmLi2MgHn, SmLi2MgHn, EuLi2MgHn, GdLi2MgHn, TbLi2MgHn, DyLi2MgHn, HoLi2MgHn, ErLi2MgHn, TmLi2MgHn, YbLi2MgHn, LuLi2MgHn, HfLi2MgHn, TaLi2MgHn, ReLi2MgHn, OsLi2MgHn, and IrLi2MgHn (here n is an integer having a value in a particular compound of 4-7) as solid hydrides for the storage and release of hydrogen. Different hydrogen contents may be obtained in compounds having the same XLi2Mg crystal structures. These materials offer utility for hydrogen storage systems.