THERMAL DIFFUSION DYNAMIC BEHAVIOR OF TWO-DIMENSIONAL Ag-SMALL CLUSTERS ON Ag(1 1 1) SURFACE

Abstract

In this paper, the thermal diffusion behavior of small two-dimensional Ag -islands on Ag (1 1 1) surface has been explored using molecular dynamics (MD) simulations. The approach is based on semi-empirical potentials. The key microscopic processes responsible for the diffusion of Ag 1−5 adislands on Ag (1 1 1) surface are identified. The hopping and zigzag concerted motion along with rotation are observed for Ag one-atom to three-atom islands while single-atom and multi-atom processes are revealed for Ag four-atom and five-atom islands, during the diffusion on Ag (1 1 1) surface. The same increasing/decreasing trend in the diffusion coefficient and effective energy barrier is observed in both the self learning kinetic Monte Carlo (SLKMC) and MD calculations, for the temperature range of 300–700 K. An increase in the value of effective energy barrier is noticed with corresponding increase in the number of atoms in Ag -adislands. A reasonable linear fit is observed for the diffusion coefficient for studied temperatures (300, 500 and 700 K). For the observed diffusion mechanisms, our findings are in good agreement with ab initio density-functional theory (DFT) calculations for Al / Al (1 1 1) while the energy barrier values are in same range as the experimental values for Cu / Ag (1 1 1) and the theoretical values using ab initio DFT supplemented with embedded-atom method for Ag / Ag (1 1 1).