Interactions between adatoms on metal surfaces will be examined using the field ion microscope to investigate chemical and structural factors in pair interactions, many-atom interactions and overlayer stability, and interactions and surface diffusion. The dependence of pair energetics upon the chemical identity of the adatoms will be explored with pairs of palladium and gold atoms on tungsten. Measurements of cluster dissociation for iridium and palladium on tungsten will be combined with data on pair interactions to determine the role of many-atom effects in cohesion. Diffusion in a surface layer containing many adatoms will be studied by measuring the time correlation of concentration flucturations to establish the effects of interaction on the diffusivity.
