DFT study of Au self-diffusion on Au(001) in the presence of a Cl adlayer

Abstract

The atomic-scale mechanism of self-diffusion on coinage metal surfaces has been investigated by density functional theory calculations before. However, the detailed role of the co-adsorbed anions and of the electrochemical interface is not yet fully understood. We present diffusion paths of a Au adatom on c(2 × 2)-Cl and c(2×22)R45◦-Cl Au(001) surfaces. In the case of the fully Cl covered Au(001) surfaces, the diffusion energy barriers are ≥0.44 eV. In the presence of a neighboring Cl vacancy, the diffusion barriers are drastically reduced to about half of the value for the fully Cl covered surface. Thus, Au self-diffusion is promoted by Cl vacancies. A first estimate for the effect of water on the diffusion energy barrier of the Cl vacancy is derived by calculating the interaction of configurations along the diffusion path with a water layer.