Structure and Bonding of Titanium Alanate

Titanium alanate Ti(AlH4)4 is a candidate material for high-density hydrogen storage that thus far has been scarcely investigated. This study determines the low energy structures of Ti(AlH4)4 by adopting a global optimization algorithm combined with density functional theories, and systematically compares their stabilities, electronic structures, and bonding properties with Mg(AlH4)2 and Ca(AlH4)2. Compared to other compounds, Ti(AlH4)4 is less stable and the Ti-H bond is of covalent nature with strong polarities. The covalent Ti-H interaction can weaken the Al-H bonds. Because both the ionic and covalent interactions of the Al-H bonds are the weakest in Ti(AlH4)4, it is favorable for the desorption of hydrogen. In this study, we determine the low energy structures of Ti(AlH4)4 and investigate their stabilities, electronic structures, and bonding properties. Ti(AlH4)4 is less stable and the covalent Ti-H interaction can weaken the Al-H bonds. Because both the ionic and covalent interactions of the Al-H bonds are the weakest in Ti(AlH4)4, it may be a promising hydrogen storage material. image