Soft X-ray emission studies on the metal-hydrogen bonding states in vanadium-based ternary hydrides

The nature of electronic or chemical bonding between hydrogen and metal atoms was studied for ternary hydrides Vsub(1-x)Msub(x)Hsub(y) (M equivalent to Fe, Cr, Ti). The soft X-ray L3 emission spectra of vanadium, iron, chromium and titanium were measured for various alloy compositions and hydrogen contents. The emission spectra of the binary alloys can be reasonably interpreted in terms of a rigid band model. However, the spectra of the ternary hydrides cannot be explained satisfactorily by this model. In these hydrides the V L3 and Ti L3 spectra deform with new substructures appearing at 7-8 eV below the emission edges, while the Fe L3 and Cr L3 spectra change little. These substructures are believed to be associated with the formation of V-H or Ti-H bonding states involving V (3d)(4s) or Ti (3d)(4s) and H 1s states. Presumably such bonding states are not formed between iron or chromium and hydrogen atoms. An inspection of the present data suggests that the formability of the chemical bonding increases in the order, iron and chromium, then vanadium and finally titanium. (Auth.)