Hydrogen sites analysed by X-ray synchrotron diffraction in Mg 7TiH 13 –16 made at gigapascal high-pressures

Abstract

The structure of a new hydrogen rich Mg-based transition metal hydride, i.e. Mg 7TiH 16, was investigated with high-energy X-ray synchrotron radiation data from the facility SPring-8, Japan. The hydride phase was in advance prepared at 8 GPa and 873 K with a cubic anvil press. The high-energy beam also enabled hydrogen to be observed. With the Rietveld method the best result was obtained when two tetrahedral sites are fully occupied by hydrogen atoms with a minimum H H distance of 1.8 Å. A sample that had been stored for a longer time before analysis appeared to have less hydrogen corresponding to the formula unit of Mg 7TiH 13 and also a smaller unit cell volume.