Fitting EXAFS data using molecular dynamics outputs and a histogram approach
Bruce D. Ravel, Stephen W. Price, Nicholas Zonias, Chris-Kriton Skylaris, Andrea Russell
It has been shown that for highly disordered systems, EXAFS underestimates coordination number and thus particle size when compared with the theoretical coordination number based on size determination from other experimental techniques1-4. Similarly, when cross-correlating EXAFS with other techniques, such as TEM and XRD5, 6, EXAFS gives smaller sizes. The failure to accurately measure the coordination number is due to a failure to account for the high degree of disorder present. The most common approach to analysing the EXAFS involves quantifying the atom-atom pair distribution extracted from the data by approximating it to a Gaussian or near-Gaussian distribution. This allows for the determination of an average coordination number, relative position from the absorber and the mean square relative disorder, MSRD (also called σ2 or the EXAFS Debye Waller term), of the absorbing atoms at that distance to be measured. If the Gaussian distribution becomes skewed, sharpened or flattened, additional terms (known as higher cumulants) can be added to the fitting parameters to account for this disorder7-9, although the use of these has limitations.
, Price, S.
, Zonias, N.
, Skylaris, C.
and Russell, A.
Fitting EXAFS data using molecular dynamics outputs and a histogram approach, Physical Review B, [online], https://doi.org/10.1103/PhysRevB.85.075439
(Accessed March 2, 2024)