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

Highlights: • The first four EXAFS cumulants are expressed in explicit and simple forms. • The obtained results are convenient and reduce measurement in analyzing EXAFS data. • The third cumulant plays an important role in the EXAFS phase shift. • The fourth cumulant has a significant influence on the EXAFS amplitude reduction. • The numerical results for Ni agree well with those obtained using other methods. 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.