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O: Oberflächenphysik
O 40: Oxides and insulators
O 40.2: Vortrag
Donnerstag, 30. März 2006, 15:15–15:30, WIL A317
A Combined DFT/LEED-Approach for Complex Oxide Surface Structure Determination: Fe3O4(001) — •R. Pentcheva1, J. Rundgren2, S. Frank1, D. Schrupp3, M. Scheffler4, and W. Moritz1 — 1Section Crystallography, University of Munich — 2Physics Dept., Royal Institute of Technology, Stockholm — 3Dept. of Physics, University of Augsburg — 4Fritz-Haber-Institut der MPG, Berlin
The structural determination of complex oxide surfaces is a challenge for quantitative analysis techniques such as XRD or LEED. Density functional theory (DFT) total energy calculations provide a mean to compare the stability of different configurations. Still, for complex structures, when many atoms relax (e.g. 50-100 degrees of freedom) the energy landscape may be rather flat and/or corrugated. In this paper we show that a multi-technique approach (employing DFT→LEED→DFT) is indeed most usefull: In the framework of ab initio thermodynamics we compiled a surface phase diagram of Fe3O4(001) for a variety of surface terminations. The novel (so far ignored) Jahn-Teller distorted, oxygen-rich surface structure predicted from the DFT-calculations [1] is confirmed by a LEED I/V (and XRD) analysis. Only the here put forward combined DFT-LEED-DFT approach where the atomic positions obtained from DFT were used as input for the LEED structural refinement and vice versa enables us to achieve a quantitative agreement between the different methods. Furthermore, we explored the influence of phase shifts obtained from the DFT-electron density for magnetite bulk and surface as opposed to conventional phase shifts.
[1] R. Pentcheva, et al., Phys. Rev. Lett. 94,126101 (2005).