title: Structure of the hydrated alpha-Al(2)O(3) (0001) surface
abstract: The physical and chemical properties of the hydrated alpha-Al(2)O(3) (0001) surface are important for understanding the reactivity of natural and synthetic aluminum-containing oxides. The structure of this surface was determined in the presence of water vapor at 300 kelvin by crystal truncation rod diffraction at a third-generation synchrotron x-ray source. The fully hydrated surface is oxygen terminated, with a 53% contracted double Al layer directly below. The structure is an intermediate between alpha-Al(2)O(3) and gamma-Al(OH)(3), a fully hydroxylated form of alumina. A semiordered oxygen layer about 2.3 angstroms above the terminal oxygen layer is interpreted as adsorbed water. The clean alpha-Al(2)O(3) (0001) surface, in contrast, is Al terminated and significantly relaxed relative to the bulk structure. These differences explain the different reactivities of the clean and hydroxylated surfaces.
authors.affiliation: Consortium for Advanced Radiation Sources, The University of Chicago, Chicago, IL 60637, USA. Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305-2115, USA. Stanford Synchrotron Radiation Laboratory, Sta.
authors.initials: PJ
authors.lastname: Eng
authors.initials: TP
authors.lastname: Trainor
authors.initials: GE
authors.lastname: Brown
authors.initials: GA
authors.lastname: Waychunas
authors.initials: M
authors.lastname: Newville
authors.initials: SR
authors.lastname: Sutton
authors.initials: ML
authors.lastname: Rivers