Atomic-scale structure of β-FeOOH containing chromium by anomalous X-ray scattering coupled with reverse Monte Carlo simulation

Ordinary X-ray diffraction and anomalous X-ray scattering (AXS) measurements below Fe K and Cr K absorption edge were carried out for characterizing the atomic-scale structure of β-FeOOH particles with and without chromium. The realistic atomic-scale structures in these β-FeOOH particles were estimated by fitting both the ordinary and environmental interference functions through reverse Monte Carlo (RMC) simulation technique. The results showed that the linkages of FeO6 octahedral structural units in the β-FeOOH particles with chromium were considerably deviated from the ideal β-FeOOH structure, whereas the fundamental structure of the β-FeOOH particles without chromium was similar to the ideal β-FeOOH case. The atomic-scale structure of the β-FeOOH particles is likely to be distorted by the substitution of chromium for iron site in the β-FeOOH structure, although the structure may also be influenced by other foreign ions.