An ab initio analysis of adsorption and diffusion of silver atoms on alumina surfaces

The adsorption and diffusion of silver adatoms on a variety of different surface terminations of alumina was studied with density functional theory. Both Al and O terminated surfaces of α-Al2O3(0001), as well as hydroxylated versions of these surfaces, were examined. The results indicate that Ag bonds weakly to the Al terminated surface and has low barriers for diffusion. This suggests that the diffusion of Ag on the alumina terminated surface is very rapid. Ag bonds much more strongly, however, to the O-terminated surface which results in higher diffusion barriers. Calculations for Ag on hydroxylated surfaces indicate that the presence of water serves to lower barriers to diffusion for Ag atoms as compared to the oxygen terminated surface but decreases diffusion as compared to the aluminum terminated surface. The results described herein help to provide a more detailed understanding of the observed surface wetting of other transition metals upon hydroxylated alumina surfaces.