Compact surface-cluster diffusion by concerted rotation and translation

Abstract

First-principles calculations show that a pseudomorphic Ir monolayer on Ir(111) has an unexpected metastable on-top configuration only slightly above the stable fcc configuration. The energy required for any translation of the monolayer parallel to the surface is small. This opens the possibility that whole clusters can move by rotation and/or translation through configurations with many atoms in on-top sites. One such diffusion mechanism, the “cartwheel shuffle” could explain otherwise mysterious long jumps and high prefactors seen in the diffusion of 19-atom Ir clusters on Ir(111).