Atomic structure and stability of magnetite Fe3O4(001): An X-ray view

B. Arndt, R. Bliem, O. Gamba, J. E. S. van der Hoeven, H. Noei, U. Diebold, G. S. Parkinson, A. Stierle

DESY NanoLab, Deutsches Elektronen-Synchrotron (DESY), D-22607 Hamburg, Germany
Physics Department, University of Hamburg, D-20355 Hamburg, Germany
Institut für Angewandte Physik, Technische Universität Wien, 1040 Wien, Austria
Debye Institute for Nanomaterials, Utrecht University, 3508 TA Utrecht, The Netherlands

Surf. Sci. 653 (2016) 76-81

The structure of the Fe3O4(001) surface was studied using surface X-ray diffraction in both ultra-high vacuum, and higher-pressure environments relevant to water-gas shift catalysis. The experimental X-ray structure factors from the (√2 × √2)R45° reconstructed surface are found to be in excellent agreement with the recently proposed subsurface cation vacancy (SCV) model for this surface (Science 346 (2014), 1215). Further refinement of the structure results in small displacements of the iron atoms in the first three double layers compared to structural parameters deduced from LEED I-V experiments and DFT calculations. An alternative, previously proposed structure, based on a distorted bulk truncation (DBT), is conclusively ruled out. The lifting of the (√2 × √2)R45° reconstruction upon exposure to water vapor in the mbar pressure regime was studied at different temperatures under flow conditions, and a roughening of the surface was observed. Addition of CO flow did not further change the roughness perpendicular to the surface but decreased the lateral correlations.

Corresponding author: Andreas Stierle. Reprints also available from Gareth S. Parkinson (parkinson at iap_tuwien_ac_at).

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