Cubic Metallic Phase of Aluminum Hydride Showing Improved Hydrogen Desorption

AlH$_3$ is of great interest for hydrogen storage applications, with a particularly attractive feature being its large hydrogen capacity of 10 wt.\%. Here we report the results of our density functional theory study of the dehydrogenation properties in a cubic phase of AlH$_3$. The metallic nature of the electronic structure entails a more favorable hydrogen removal energy which is lowered by 75\% compared to the insulating hexagonal phase. This remarkable reduction in the Al--H bond strength might bear important consequences for feasible applications of AlH$_3$ as an on-board hydrogen storage material for mobile applications. Suggestions are made how the cubic phase could be prepared and stabilized at ambient pressure by off-board quenching. See also: R.\ H.\ Scheicher, D.\ Y.\ Kim, S.\ Leb\`egue, B.\ Arnaud, M.Alouani, and R.\ Ahuja, {\it Appl.\ Phys.\ Lett.} {\bf 92}, 201903 (2008) and D.\ Y.\ Kim, R.\ H.\ Scheicher, and R.\ Ahuja, {\it Phys.\ Rev.\ B} {\bf 78}, 100102(R) (2008).