Analysis of EXAFS oscillation of FCC crystals using classical anharmonic correlated Einstein model

Abstract

In this work, we analyze the extended X-ray absorption fine structure (EXAFS) oscillation of face-centered cubic crystals based on the classical anharmonic correlated Einstein (CACE) model and suitable analysis procedure. The calculation of EXAFS cumulants is performed by the CACE model, where thermodynamic parameters are derived from the anharmonic effective potential that depends on the crystal structure type and obtained using the first shell near-neighbor contribution approach. Temperature and wavenumber dependence of the anharmonic EXAFS oscillation is analyzed via evaluating the contributions of the cumulants to the phase shift and amplitude reduction, in which the anharmonic EXAFS oscillation is presented in terms of the Debye-Waller factor up to the fourth-order using the cumulant expansion approach. The numerical results for crystalline nickel are found to be in good agreement with those obtained from the experiments and other theoretical methods at various temperatures. This model is very effective for analyzing experimental EXAFS data of the anharmonic EXAFS signals above the correlated Einstein temperature.