Theoretical Calculation of Finite Temperature X Ray Absorption Fine Structure Application to Sodium K Edge in NaCl

Abstract

This study presents a comprehensive computational framework for reproducing the full X ray absorption fine structure XAFS through quantum chemical simulations. The near edge region is accurately captured using an efficient implementation of time dependent density functional perturbation theory applied to core excitations, while ab initio molecular dynamics provides essential sampling of core excitation energies and interatomic distance distributions for interpreting extended X ray absorption fine structure EXAFS features. Owing to the efficiency of the approach, the total spectrum can be decomposed into contributions from bulk, defective, and surface environments, which commonly coexist in experimental systems. The method ology is demonstrated for sodium at the Na K edge in NaCl, where the predicted spectra show good agreement with experi mental measurements on thin film samples. This strategy offers a practical route to generating chemically specific XAFS cross section data for elements and species that remain challenging to characterize experimentally, thereby enabling deeper insights into materials of technological importanc