CO-REFINEMENT OF DIFFRACTION ANOMALOUS FINE-STRUCTURE DATA

Diffraction Anomalous Fine-Structure (DAFS) combines the sensitivity t o long-range-order of diffraction with the short-range-order sensitivi ty of XAFS. This makes it possible to use a set of DAFS measured inten sities to simultaneously refine both long-and short-range structural p arameters, while maintaining some constraints between them. This metho d combines a calculation of the structure factor based on the unit cel l of the crystal with a calculation of the fine-structure chi(E) aroun d each resonant site. Tabulated values of the scattering amplitude are used away from the resonant energies, while the near-edge anomalous s cattering amplitude is calculated for the resonant sites using a diffe rential Kramers-Kronig transform of an embedded atom absorption coeffi cient mu(0)(E) from FEFF. We discuss some of the subtleties of this ap proach to DAFS analysis.