(19f) Water Ordering at Low-Index Alumina Surfaces: Structure and Reactivity

The interaction of water with mineral surfaces is expected to play a major role in controlling chemical processes in biological, chemical, and environmental systems; for example, the water-aluminum oxide (Al₂O₃) interface governs reactions on biological implants, heterogeneous catalysts, and atmospheric nanoparticles. The clean and hydrated Al₂O₃ (1-102) and (11-20) surface structures and energetics are calculated using pseudopotential plane wave density functional theory. Since both alumina and hematite (Fe₂O₃) share the corundum structure, their surface terminations are expected to be similar. The hydrated Al₂O₃ (1-102) surface is found to be isostructural to the hydrated Fe₂O₃ (1-102) surface, but the nature of the energetically preferred surface termination is dependent on temperature. Initial structural models of the hydrated Al₂O₃ (11-20) surface are also compared to experimental data on the hydrated Fe₂O₃ (11-20) surface. These results of water ordering at alumina surfaces are an important step towards a molecular scale understanding of the factors that dictate surface structure and reactivity, which would greatly aid in the development of robust models of interfacial processes in the environment.