The crystal structure of LiMgAlD6 from combined neutron and synchrotron X-ray powder diffraction

LiMgAlH6 is the intermediate phase when LiMg(AlH4)3 is heated. It contains 9.4 wt.% hydrogen, of which 4.8 wt.% is released during the decomposition step to MgH2 and LiH. Deuterated LiMgAlD6 was prepared by heat-treating LiMg(AlD4)3 at 130 °C. Powder neutron and synchrotron X-ray diffraction patterns were measured and the structure was refined using the Rietveld technique on both patterns simultaneously. LiMgAlD6 crystallizes in the trigonal space group P321 with a = 7.9856(4) Å and c = 4.3789(3) Å. The structure consists of isolated AlD6 octahedra connected through octahedrally coordinated Mg- and Li-atoms.