Alloying effects on the electronic structure of Mg 2Ni intermetallic hydride

Abstract

The electronic structures of Mg 2Ni intermetallic hydride containing a variety of alloying elements are investigated by the DV-Xα cluster method. It is shown that the Ni Mg atomic interaction is most dominant in pure Mg 2Ni hydride. Also, the hydrogen atoms make a strong bond with Ni atoms rather than Mg atoms. Thus, both the Ni H and the Ni Mg atomic interactions are found to affect directly the phase stability of the hydride. These interactions change remarkably with alloying, when the alloying element M is substituted for the Ni atom. The significant decrease in the M Mg atomic interaction causes an instability of the hydride even in the case of increasing M H atomic interaction, resulting in the high enthalpy of formation for the hydride observed experimentally. Further, a correlation between the lattice volume and the hydriding property is discussed in terms of the nature of the chemical bond between atoms.