W0131: Including Solid-State Effects in F' and F'' Using Ab initio Calculations of X-Ray Absorption Spectra

W0131

Including Solid-State Effects in F' and F'' Using Ab Initio Calculations of X-Ray Absorption Spectra. Julie Cross, Matthew Newville, John Rehr, Larry Sorensen, Charles Bouldin, Gavin Watson, Thomas Gouder, Gerry Lander, Michael Bell, Dynamics of Solids Branch, Naval Research Laboratory, Code 6680, Washington, DC 20375 USA

Theoretical calculations of Bragg peak intensities in the vicinity of an absorption edge can be improved dramatically by including the effects of the local environment on the resonant elastic scattering amplitudes. We have obtained improved resonant (anomalous) scattering amplitudes f' and f'' by applying a differential Kramers-Kronig transform to theoretical calculations of x-ray absorption cross-sections by the computer program FEFF. We present the results of using these improved amplitudes in a kinematic structure factor calculation to model diffraction fine-structure data (DAFS) from YBa₂Cu₃O_7-d at the Cu K resonance and UO₂ at the U M_IV resonance. Our results on these systems indicate that the dominant features in the DAFS spectrum are accounted for by the XAFS multiple scattering approach.