Co-refinement of diffraction anomalous fine-structure data

Diffraction Anomalous Fine-Structure (DAFS) combines the sensitivity to long-range-order of diffraction with the short-range-order sensitivity of XAFS. This makes it possible to use a set of DAFS measured intensities to simultaneously refine both long- and short-range structural parameters, while maintaining some constraints between them. This method combines a calculation of the structure factor based on the unit cell of the crystal with a calculation of the fine-structure χ(E) around each resonant site. Tabulated values of the scattering amplitude are used away from the resonant energies, while the near-edge anomalous scattering amplitude is calculated for the resonant sites using a differential Kramers-Krönig transform of an embedded atom absorption coefficient μ₀(E) from FEFF. We discuss some of the subtleties of this approach to DAFS analysis.