Anharmonic effects and EXAFS of hcp crystals studied based on high-order expanded Debye-Waller factors including dispersion effects

The anharmonic effects and extended X-ray absorption fine structure (EXAFS) of hcp crystals have been studied based on the high-order expanded Debye-Waller factors. The theory is derived based on the many-body perturbation approach and cumulant expansion up to the fourth order with using the linear anharmonic oscillator model to account for the dispersion involving more contributions of phonons from the first Brillouin zone. The derived anharmonic effective potential includes the many-body effect by a simple measure avoiding the intensive full lattice dynamical calculations. The Morse potential is assumed to describe the single-pair atomic interaction. The derived analytical expressions for cumulants describe the anharmonic effects and are applied to the anharmonic EXAFS contributing to the accurate structural determination. The advantages and efficiencies of the present theory are illustrated by good agreement of numerical results for all considered quantities of Zn in hcp phase with experiment. •Anharmonic effects and EXAFS of hcp crystals studied based on high-order expanded Debye-Waller factors.•The research model is derived using the many-body perturbation and cumulant expansion approaches.•Strong dependence of considered quantities on dispersion involves more contributions of phonons.•Derived cumulants included in anharmonic EXAFS contribute to accurate structural determination.•Numerical results of all considered EXAFS quantities of Zn (hcp) agree well with experiment.