Comparison of the wet hematite and corundum (0001) surface structures determined by synchrotron x-ray CTR analysis

Glenn Waychunas, Thomas Trainor, Peter Eng, and Gordon Brown

Contact: Glenn Waychunas, 510/495-2225, GAWaychunas@lbl.gov

Research Objectives
The surfaces of crystalline minerals generally differ from the bulk structure due to atomic relaxation, expansion, or rearrangement. These changes can have profound effects on the reactivity of the mineral, especially with regard to toxics sorption, catalytic activity, and dissolution. Although modern thermodynamic calculations and structural simulations are now well developed, these still rest on the fundamental underpinning of the experimental determination of the true surface structure. Here we focus on two isostructural phases that behave quite differently in the environment. Hematite is a primary soil mineral with much greater reactivity than corundum. Though itself not found in soils, the corundum (0001) surface structure is a much-used analog for the alumina layers in clays, which also has relatively low reactivity. The aim is to uncover a structural basis for the differences in reactivity.

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