Atomistic calculations were performed on a slab model of the (0001) surface of hematite as well as the bulk structure. In particular, the energetics of oxygen vacancies near the surface was studied. Atomistic modeling was used to establish the defect energies in the bulk versus distance from the surface. Transition state calculations were performed to compute barriers for several pathways of migration of oxygen vacancies in the bulk and at varying depths relative to the surface. We find energy barriers of several transitions considerably lowered closer to the surface. Considerations of literature data for electrical conductivity and Seebeck coefficient on bulk versus thin-film hematite suggest high populations of point defects near surfaces, in agreement with our predictions.

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We report the synthesis and characterization of non-d 10 p-type transparent conducting oxides of the normal spinel ZnRh 2 O 4 . Undoped ZnRh 2 O 4 was successfully prepared by means of bulk solid-state synthesis. The conduction mechanism and bulk defect chemistry of polycrystalline sintered pellets of ZnRh 2 O 4 were studied through electrical conductivity and Seebeck coefficient measurements, in defect equilibrium at elevated temperature under controlled atmospheres. Optical diffuse reflectance measurements were also carried out to evaluate band gap. The data were analyzed in terms of an activated mobility ͑small polaron conduction͒, with a hopping energy of 0.25 eV. Results from band structure calculations by LDA+ U and optical band-gap measurement by UV-visible spectrometry are in good agreement with literature data.

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