Temperature-Dependent EXAFS Debye–Waller Factor of Distorted HCP Crystals

Abstract

In this paper, an efficient theoretical model has been developed to calculate and analyze the extended X-ray absorption fine structure (EXAFS) Debye–Waller factor (DWF) of distorted hexagonal close-packed (HCP) crystals with non-ideal axial ratio c/a in the temperature dependence. The analysis procedure is performed by evaluating the influence of temperature on the amplitude reduction and phase shift of EXAFS oscillation that is expressed in terms of EXAFS DWF using EXAFS cumulants in the cumulant expansion approach. The calculation model of the temperature-dependent EXAFS cumulants is expanded from the correlated Einstein model using the classical statistical theory and the anharmonic effective potential that depends on non-ideal axial ratio c/a of distorted HCP crystals. The numerical results for crystalline zinc agree well with those obtained from other theoretical methods and experiments at various temperatures. The obtained results show the present theoretical model is necessary to analyze and evaluate the temperature-dependent experimental EXAFS signals of distorted HCP crystals under the effect of non-ideal axial ratio c/a.