Structure of the hydrated alpha-Al(2)O(3) (0001) surface
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.
Eng
PJ
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.
Trainor
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Brown
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Waychunas
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Newville
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Sutton
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Rivers
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