Design of hydrogen storage alloys with the aid of molecular orbital method

Abstract

The electronic structures of hydrogen storage alloys are calculated by the DV-Xα molecular orbital method. The results revealed that hydrogen interacts more strongly with hydride-non-forming elements, B, (e.g. Ni, Mn, Fe) than hydride-forming elements, A, (e.g. La, Zr, Ti, Mg) in every hydrogen storage alloy, despite there being a larger affinity of A elements for hydrogen than B elements in the binary metal-hydrogen system. The presence of such a metal-hydrogen interaction is a characteristic of hydrogen storage alloys. Furthermore, the A/B compositional ratio of hydrogen storage alloys can be understood in terms of a simple parameter, 2Bo(A-B)/[Bo(A-A)+Bo(B-B)], where the Bo(A-B), Bo(A-A) and Bo(B-B) are the bond orders between atoms given in the parentheses.