Fitting Multiplet Simulations to L-Edge XAS Spectra of Transition- Metal Complexes Using an Adaptive Grid Algorithm

A new methodology based on an adaptive grid algorit h m followed by an analysis of the ground state from the fit parameter s is presented to analyze and interpret experimental XAS L2,3-edge data. The fitting method is tested first in a series of multiplet calculations for d0-d7 systems and for which the solution is known. In most cases, the algorit h m is able to find the solution, except for a mixed-spin Co2+ Oh complex, where it instead revealed a correlation between the crystal field and the electron repulsion parameter s near spin-crossover transition points. Furthermore, the results for the fitting of previously published experimental data sets on CaO, CaF2, MnO, LiMnO2, and Mn2O3 are presented and thei r solution discussed . The presented methodology has allowed the evaluation of the Jahn-Teller distortion in LiMnO2 , which is consistent with the observed implications in the development of batteries, which use this material. Moreover, a follow-up analysis of the ground state in Mn2O3 has demonstrated an unusual ground state for the highly distorted site which would be impossible to optimize in a perfect octahedral environment. Ultimately, the presented methodology can be used in the analysis of X-ray absorption spectroscopy data measured at the L2,3-edge for a large number of materials and molecular complexes of first-row transition metals and can be expanded to the analysis of other X-ray spectroscopic data in future studies.

Automated summary

A new methodology based on an adaptive grid algorithm followed by an analysis of the ground state from the fit parameters is presented for analyzing and interpreting experimental XAS L2,3-edge data. The methodology was tested on known solutions and successfully found the solution for most cases. The methodology was then applied to fitting previously published experimental data sets and resulted in meaningful solutions.