Decay Kinetics of Cluster-Beam-Deposited Metal Particles

High-precision experiments and atomistic simulations are used to determine the flattening kinetics of mass-selected 55-147 atom Ag clusters deposited on Au(111). The clusters are shown to align epitaxially and decay through an exchange pathway with a range of rate-limiting barriers, from ca. 0.25 to 0.4 eV, depending on the shape of the particle. It is also shown that nonlocal effects at the Au-Ag interface lead to a dramatic reduction in the barrier of the dominant transition pathway, requiring ab initio methods for correct modeling. As a result, quantitative correspondence between experimental and simulated island heights is obtained.