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.