(144j) Accelerated Molecular Dynamics Investigation of the Rapid Diffusion of Large Heteroepitaxial Islands

In this work, we use parallel replica dynamics to extend molecular dynamics simulations to longer timescales and lower temperatures in order to investigate the diffusion of Ag monolayer islands on Cu(001) surfaces. An analysis of several low-energy pathways reveals two governing processes: a rapid, glide-centric process and a slower, vacancy-assisted one. It should be noted that this cooperative mechanism was observed for very large islands for which diffusion was orders of magnitude faster than for single Ag atoms below room temperature. In addition, the nudged elastic band technique is used to calculate activation barriers; thus, determining the rate-limiting steps in diffusion of the islands.

Our findings should provide insight to future experimental research on the size distribution and shapes observed during the growth of thin films in similar systems. Furthermore, these results should have implications for Monte Carlo models of film growth which generally allow only single atom diffusion, thus neglecting such complex, cooperative mechanisms.