Charging effects on the adsorption and diffusion of au adatoms on MgO(100)

By ab initio calculations, the adsorption and diffusion properties of positively charged Au⁺ and negatively charged Au− adatoms on defect-free MgO(100) surfaces were investigated and compared with the case of charge-neutral Au⁰ on MgO(100). Our results showed that the most stable adsorption site of Au⁺ on MgO(100) is atop the O site, as per Au⁰, whereas that of Au⁻ on MgO(100) is atop the Mg site. Our results showed a surface diffusion barrier of Au⁺ on MgO(100) of 0.30 eV, which is larger than that (0.25 eV) of Au⁰. For Au⁻, the surface diffusion barrier is as low as 0.03 eV. Further detailed analyses of the charge rearrangement, Bader charges, electronic structures, and characteristics of the atomic bonds were also performed. These results emphasize the significant roles of the charge states of Au adatoms in the adsorption and diffusion properties of Au on MgO(100).