Multiple-scattering calculations of x-ray-absorption spectra

TLDR

The authors present a high‑order multiple‑scattering method for polarized x‑ray‑absorption spectra that simultaneously treats XAFS and XANES. The method employs a curved‑wave multiple‑scattering formalism that discards negligible paths, incorporates energy‑dependent self‑energy and Debye‑Waller factors, and includes embedded‑atom background absorption, and is demonstrated on Cu, Cd, and Pt. For these metals the expansion converges to experimental accuracy using only a few dozen dominant paths—primarily single‑scattering, focusing, linear, and triangular—matching both experiment and full multiple‑scattering calculations.

Abstract

A high-order multiple-scattering (MS) approach to the calculation of polarized x-ray-absorption spectra, which includes both x-ray-absorption fine structure and x-ray-absorption near-edge structure, is presented. Efficient calculations in arbitrary systems are carried out by using a curved-wave MS path formalism that ignores negligible paths, and has an energy-dependent self-energy and MS Debye-Waller factors. Embedded-atom background absorption calculations on an absolute energy scale are included. The theory is illustrated for metallic Cu, Cd, and Pt. For these cases the MS expansion is found to converge to within typical experimental accuracy, both to experiment and to full MS theories (e.g., band structure), by using only a few dozen important paths, which are primarily single-scattering, focusing, linear, and triangular.