Email: cynthia.lo@nist.gov Web: http://www.staff.uaf.edu/fncsl/

The structure of hydrated hematite (α-Fe₂O₃) has been investigated by density functional theory and ab initio thermodynamics. The hydrated α-Fe₂O₃ (1-102) surface has zero occupancy of the top layer of iron atoms, and apparent double protonation of the top layer of oxygen atoms. This structure is the most energetically stable across the entire range of experimentally accessible oxygen chemical potentials, and is the best-fit model to experimental crystal truncation rod diffraction data. Future studies will focus on the hydrated α-Fe₂O₃ (11-20) and (1010) surfaces, goethite, and magnetite.