Density Functional Theory Investigations on the Structure and Reactivity of Aqueous Hematite (a-Fe2O3) Surfaces
Cynthia S. Lo and Anne M. Chaka
Physical and Chemical Properties Division
Chemical Sciences and Technology Laboratory
Building 222, Room A157, Mail Stop 8380
Tel: (301) 975-5478, Fax: (301) 975-3672
Sigma Xi Member (2000)
January 14, 2005
The reactivity of a mineral surface depends on several factors, including the composition of the bulk material, crystallographic orientation, local coordination of the surface atoms, and topographic arrangement of the surface functional groups. In particular, the interaction of corundum-type metal oxide surfaces with water is not well understood, because the majority of experimental and theoretical data has been on the corresponding UHV-prepared or clean surfaces. These interactions play major roles in environmental processes, including contaminant sequestration, mobility, and remediation, and biogeochemical cycling of contaminants and nutrients.
We have focused our studies on investigating the structure/reactivity relationship of iron oxide surfaces under conditions encountered in environmental settings. We present density functional theory studies of the structure of clean and hydroxylated a-Fe2O3 (0001) and a-Fe2O3 (1-102), and the various H and metal coordinations leading to the lowest surface free energies. We also compare the stability of aqueous Fe to bulk Fe2O3. Finally, we compare our theoretical results to those from crystal truncation rod diffraction data.