Ab-initio study of the effects of charging on the adsorption and diffusion of Au₂ on MgO(100)

By using ab-initio calculations, the adsorption and diffusion properties of charged Au dimers (Au₂⁺ and Au₂⁻) on MgO(100) were investigated and compared with those of the charge-neutral dimer (Au₂⁰). The most favored adsorption structure of Au₂⁺ on MgO(100) is the upright dimer on a surface O atom in agreement with that of Au₂⁰. The surface diffusion of Au₂⁺ on MgO(100) occurs by the leapfrog process with a barrier height of 0.38 eV lower than that of Au₂⁰ (0.66 eV). The most stable adsorption structure of Au₂⁻ on MgO(100) is the flat-lying dimer on two surface Mg atoms. The surface diffusion of Au₂⁻ on MgO(100) can proceed by the hopping and walking processes with a barrier height in the range of 0.05–0.11 eV, which is much lower than the diffusion barriers of Au₂⁺ and Au₂⁰. Furthermore, detailed information on the electronic properties of Au₂⁰, Au₂⁺, and Au₂⁻ are also presented.