ALLOYING EFFECTS ON THE ELECTRONIC-STRUCTURE OF MG2NI INTERMETALLIC HYDRIDE

The electronic structures of Mg2Ni intermetallic hydride containing a variety of alloying elements are investigated by the DV-X alpha cluste r method. It is shown that the Ni-Mg atomic interaction is most domina nt in pure Mg2Ni hydride. Also the hydrogen atoms make a strong bond w ith Ni atoms rather than Mg atoms. Thus, both the Ni-H and the Ni-Mg a tomic 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 significan t decrease in the M-Mg atomic interaction causes an instability of the hydride even in the case of increasing M-H atomic interaction, result ing in the high enthalpy of formation for the hydride observed experim entally. Further, a correlation between the lattice volume and the hyd riding property is discussed in terms of the nature of the chemical bo nd between atoms.