Revisiting the K-edge x-ray absorption fine-structure of Si, Ge-Si alloys, and the isoelectronic series CuBr, ZnSe, GaAs, and Ge
Eric L. Shirley, Joseph Woicik
Extended x-ray absorption fine structure (EXAFS) has evolved into an unprecedented technique for local structural determination in material, chemical, and physical problems in materials science. Just as for other experimental techniques, such as x-ray and neutron diffraction, several atomic parameters must be known a priori to quantitatively determine structure. Here we revisit the problem of the atomic phase shifts and backscattering amplitudes for the isoelectronic series CuBr, ZnSe, GaAs, and Ge as studied by Stern et al. during the early development of EXAFS [Phys. Rev. B 21, 5521 (1980), Phys. Rev. B 27, 1017 (1983)]. An ab initio EXAFS code such as FEFF accurately predicts backscattering amplitudes and atomic phase shifts, which are primarily functions of the sum of atomic numbers Z in a scattering path. We also consider first- and second-shell phase transferability and problems that arise if a backscatterer is identified incorrectly. Replicating features in the near-edge (NEXAFS) region of the spectrum, on the other hand, requires a more comprehensive treatment of the density-of-states, including effects of the screened Coulomb interaction between the photoelectron and its core hole. The Bethe-Salpeter equation (BSE) accurately predicts the NEXAFS for the isoelectronic series in addition to Si and Ge-Si alloys, including within a few eV of the absorption edge, where band structure effects are most important.
and Woicik, J.
Revisiting the K-edge x-ray absorption fine-structure of Si, Ge-Si alloys, and the isoelectronic series CuBr, ZnSe, GaAs, and Ge, Physical Chemistry Chemical Physics, [online], https://doi.org/10.1039/d2cp00912a, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=934096
(Accessed September 21, 2023)