We use first-principles density functional theory to investigate adsorption of Al, O, Hf, Y, Pt, and S-atoms on the α-Al2O 3(0001) surface. We identify stable adsorption sites and predict binding energies and structures. We find that Al, Hf, and Y preferentially adsorb on threefold-hollow sites, transfer electrons to the surface, and form ionic bonds to the three oxygen atoms. In contrast, the most stable adsorption site for Pt and S is ontop an oxygen atom, and we do not observe significant charge transfer. We find a binding order of S < Pt < O < Al ≪Y < Hf, which reflects both the ease with which the early transition metals Hf and Y ionize, as well as the (nearly) closed-shell repulsions influencing the adsorption of O, Pt, and S. We use these results to rationalize some observations regarding the stability of thermal barrier coatings.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films