Electronic characterization and reactivity of bimetallic clusters of the Ti(Mg)_n type for hydrogen storage applications

This paper describes the variations in the properties, characteristics and hydrogenation energy barriers of magnesium clusters induced by titanium. DFT approach was used to determine the most stable structures at this theory level and then MP2 was used to refine the energy calculations with the basis set 6-311g(d) for magnesium and hydrogen, and pseudopotential lanl2dz for titanium. Bimetallic clusters showed higher stability and reactivity than the corresponding magnesium ones. Titanium induces a change in the magnesium atoms in their electronic configuration reflected in an increase of the population of their orbitals. At the same time titanium electronic populations is modified. These changes cause variations in some reactivity parameters such as the Fukui indexes which modify the hydrogenation of the magnesium clusters and bimetallic clusters. For example, there is a reduction in the energy barrier for dissociation of the H₂ molecule in the bimetallic clusters. In the hydrogenated cluster the hydrogen atoms form bridges between all of the magnesium or magnesium-titanium atoms. These results indicate that, energetically, bimetallic systems can be more promising systems for hydrogen storage.