Automatic Atomic Structure Determination Through X-Ray Absorption Spectroscopy (EXAFS)

Extended x-ray absorption fine structure (EXAFS) has become a widely used technique for atomic structure determination. Fourier transformation connects EXAFS in k-space and R-space. However, determining the appropriate k range for the transformation can be challenging. In this study, we present an automatic method to determine the k range using the Larch package and a Python program. The first step is to evaluate the maximum value in the k range (k_max) by estimating noise for different k_max values. The k_max is determined by applying an empirical noise threshold of the second derivative of the noise, which is the point the noise level changes dramatically. Using the obtained k_max value, the first shell is then modeled to determine E₀and to estimate the minimum value for the k range (k_min) through the R-factor of the fit. The k_min value is identified as the point where the R-factor is minimized. Our method was tested on various typical data sets and resulted in suitable k ranges for Fourier transformation and accurate first-shell fitting. This approach helps to avoid unreliable and irreproducible data analysis, especially for noisy data from the diluted samples.