Local Structure of Cr-Doped Hematite: Multiedge EXAFS Analysis Using Evolutionary Algorithm/Reverse Monte Carlo Simulations

• Published in: Journal of physical chemistry. C Vol. 129; no. 32; pp. 14638 - 14645
• Main Authors: Annadata, Harshini V, Tripathi, V. M., Pai, Mrinal R., Banerjee, Atindra Mohan, Ghosh, Biplab
• Format: Journal Article
• Language: English
• Published: American Chemical Society 14.08.2025
• Subjects: C: Physical Properties of Materials and Interfaces
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.5c04306

Hematite (α-Fe2O3) is widely studied for catalysis, yet local structural effects upon doping with Cr remain elusive. We use extended X-ray absorption fine structure (EXAFS) at Fe and Cr K-edges with reverse Monte Carlo evolutionary algorithm (RMC-EA) simulations to resolve the impact of Cr in Fe1.8Cr0.2O3 when compared to Fe2O3. EXAFS confirmed that Cr3+ substitutes for Fe3+ in octahedral sites, while RMC-EA modeling reveals that Cr doping reduces the interquartile range (IQR) of Fe–O bond lengths, indicating a more uniform and less disordered Fe–O coordination environment despite an unchanged average bond length. Synchrotron X-ray diffraction confirms phase integrity, but the RMC-EA simulation provided an understanding that the Fe–O network is constrained by the presence of chromium. This study highlights the capability of RMC-EA-EXAFS to reveal subtle but significant dopant-induced changes in the local structural order that are masked by conventional analysis based on averages.