Atomic mechanisms of cluster diffusion on metal fcc(1 0 0) surfaces

We study atomic mechanisms of diffusion of small adatom islands on fcc(1 0 0) metal surfaces using semi-empirical embedded-atom model and glue potentials for Cu and Al, respectively. We focus on the role of many-body mechanisms of cluster motion which can contribute to low temperature crystal growth. Combination of systematic saddle-point search methods with molecular statics simulations allows us to find all the relevant transition paths for cluster motion on a flat surface. For both Cu and Al, we find several low-energy concerted mechanisms including row shearing and dimer rotation. Moreover, we demonstrate the existence of a new low energy mechanism for embedding an adatom into a cluster which can contribute to interlayer transport at low temperatures. We also study the role of exchange processes on the Al(1 0 0) surface.