J. Phys. IV France 7 (1997) C2-759-C2-760
Co-Refinement of Diffraction Anomalous Fine-Structure DataM. Newville1, J.O. Cross2, B. Ravel3, L.B. Sorensen3, C.E. Bouldin4 and Y. Yacoby5
1 Lawrence Livermore National Laboratory, L-219, Livermore CA 94550, U.S.A.
2 Naval Research Laboratory, Code 6680, Washington DC 20375, U.S.A.
3 Department of Physics, Box 351560, University of Washington, Seattle, WA 98195, U.S.A.
4 National Institute of Standards and Technology, Gaithersburg MD 20899, U.S.A.
5 Racah Institute of Physics, Hebrew University, Jerusalem, Israel
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 X(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.
© EDP Sciences 1997