Multiple solutions in data fitting: a trap in EXAFS structural analysis and some ideas to avoid it.

Area of Science:

• Materials Science
• Analytical Chemistry
• Spectroscopy

Background:

• Extended X-ray Absorption Fine Structure (EXAFS) is a powerful technique for determining local atomic structure.
• Accurate interatomic distance determination is crucial for understanding material properties.
• Multishell EXAFS data analysis can be complex and prone to errors.

Purpose of the Study:

• To describe a potential source of error in interatomic distance determination during EXAFS multishell data analysis.
• To investigate this error using simulated and experimental EXAFS signals.
• To discuss the origin of this specific type of error.

Main Methods:

• Simulated EXAFS signal generation for a cluster of Rhodium (Rh) atoms interacting with Oxygen (O) atoms.
• Fitting of the simulated EXAFS signal to identify potential errors.
• Analysis of an experimental EXAFS signal using similar fitting procedures.

Main Results:

• A specific error source affecting interatomic distance determination in multishell EXAFS data was identified.
• The fitting of simulated data revealed discrepancies related to the interaction between Rh and O atoms.
• The analysis of experimental data corroborated the findings from the simulated signal.

Conclusions:

• The study highlights a critical consideration for accurate EXAFS data analysis, particularly in multishell systems.
• Understanding this error source is essential for reliable interatomic distance measurements.
• This work contributes to improving the precision of EXAFS-based structural analysis.