The ability of the field ion microscope to routinely visualize individual atoms on a crystal will be utilized to quantitatively characterize different aspects of metal clusters on metal surfaces: a. Atomic Interactions and Cohesion of Clusters From measurements of the equilibrium pair distribution function, the interactions between two atoms will be determined on smooth planes of bcc as well as fcc metals. Experiments on different adatoms and on different surfaces will explore chemical and structural effects on the interactions. b. Cluster Formation and Mobility The growth and structural transformations of metal clusters will be examined on densely packed planes of fcc and bcc metals. Diffusion of clusters will be studied to establish uder what conditions motion of the cluster as a whole dominates its mobility. c. Chemical Reactivity of Clusters If time permits, the ability of metal clusters, characterized by field ion microscopy, to catalyze dissociative chemisorption will be tested on smooth planes on which chemisorption is otherwise slow.//
