Atomic-scale structure in α-FeOOH particles estimated from the anomalous X-ray scattering data with reverse Monte Carlo simulation

The realistic atomic-scale structure of synthesized α-FeOOH (goethite) particles, which is a typical ferric oxyhydroxide of corrosion product formed on the steel surface, has been estimated by fitting both the ordinary interference function and the environmental interference function obtained from the anomalous X-ray scattering (AXS) with model calculation using the reverse Monte Carlo (RMC) simulation technique. The results indicated that the FeO6 octahedral unit structure is unchanged in α-FeOOH particles with and without chromium, but distortion of the linkage of FeO6 octahedral unit structure is quite likely induced by chromium addition, where chromium is found to substitute for iron site in α-FeOOH particles. The middle-range ordering (≈nm scale) characterized by the FeO6 octahedral unit structure in α-FeOOH particles was also visualized.