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O: Oberflächenphysik

O 34: Poster (II)

O 34.99: Poster

Donnerstag, 26. März 1998, 20:00–22:30, Bereich C

The Surface Geometry of α-Fe₂O₃ (Hematite) (0001) — •Xiao-Gang Wang, Matthias Scheffler, Max Petersen, and Frank Wagner — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin-Dahlem

Despite the importance of metal oxides for several profitable industrial processes, good quality studies of surface geometries of these systems are scarce. Motivated by the previous work [1], we decided to study a corundum-type oxide surface Fe₂O₃ (0001). The surface geometry of the flat surface was unclear and even the surface stoichiometry was not known. Using density-functional theory (DFT-GGA) and employing the improved FP-LAPW method we have calculated the surface energies and structural relaxations of all (1×1) α-Fe₂O₃ (0001) surfaces. These results are analyzed with respect to the atomic chemical potential, which might be tuned in experiments by the O₂-gas pressure. The results clearly show that normally the Fe terminated surface, Fe-O₃-Fe-Fe-O₃- ⋯ , is energetically favorable. Under oxygen-rich conditions, an oxygen terminated surface, O₃-Fe-Fe-O₃- ⋯ , becomes possible. For the Fe terminated surface, we find that the first Fe layer encounters a large inwards relaxation (≈ 55%). For the subsurface O₃ layers and the top oxygen layer of the O₃ terminated surface, we find a reconstruction which has not been reported so far for corundum-type metal oxides: a small in-plane rotation.

[1] M. Ritter, H. Over, and W. Weiss, Surf. Sci. 371, 245 (1997)