Structural and diffusive properties of small 2D Au clusters on the Cu(1 1 1) surface

We present molecular dynamics simulation results concerning the structural and the diffusive properties of small (3–7 atoms) 2D Au clusters on the Cu(1 1 1) surface. We found that in the normal to the surface direction the clusters are expanded, while the surface layer is contracted, depending on the cluster size, these relaxations exhibiting power law temperature dependence. The mean-square displacements of both cluster and surface atoms increase linearly with temperature, while size dependence is found for the cluster atoms. Furthermore, the trajectory analysis revealed a lot of cluster diffusion processes among which concerted motion events, in agreement with available theoretical and experimental data. However, it comes out that the diffusion takes place mainly via mechanisms consisted of a rapid succession of sub-processes, each involving few cluster atoms. Moreover, we calculated the total atomic and cluster diffusion coefficients and we found that they exhibit Arrhenius behaviour, from where we deduced the corresponding activation energies.