Hydride vibrations in metals and metal clusters

Metal hydride cluster compounds are frequently taken to represent to some degree of approximation similar hydride bonding situations in the bulk, subsurface layers or on surfaces. These analogies have been essential for analyzing vibrational spectra of hydrogen on surfaces, for example, where the adsorption site geometry is not known. In addition, such complexes may bind hydrogen to metals that do not readily take up hydrogen in the bulk, and may thus serve as models for those hydrides as well, or they may bind hydrogen in a different coordination from that of the bulk hydride. The authors utilized inelastic neutron scattering techniques to observe hydride vibrations in some of these metals, in actinide hydrides and in several octahedral and bimetallic tetrahedral metal clusters. These observations will be discussed in terms of hydrogen-metal interactions and the applicability of the cluster analogy with the aid of idealized correlations of hydrogen vibrational frequency with hydrogen metal distance