DIMER SHEARING AS A NOVEL MECHANISM FOR CLUSTER DIFFUSION AND DISSOCIATION ON METAL (100) SURFACES

Using bond-counting arguments and embedded-atom calculations, we estab lish the crucial importance of dimer shearing in metal (100) submonola yer epitaxy. This process provides the easiest pathway for diffusion o f compact clusters of sizes 4, 6, and 8, and introduces a rich variety of localized cluster dynamics.-A combination of the dimer shear motio n and the traditional mechanism of sequential motion of individual ato ms provides a better interpretation of the oscillatory behavior of clu ster mobility with cluster size. This combination also defines a new s et of critical cluster sizes that are likely to be selected in epitaxi al growth.