ANOMALOUS SCATTERING POWDER DIFFRACTION: A VERSATILE TOOL . A. P. Wilkinson, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400

Anomalous scattering diffraction facilitates two types of experiments, i) studies requiring scattering contrast variation, and ii) crystallographic site specific X-ray absorption measurements. In principle, the latter can provide information on local coordination geometry, oxidation state and polarization dependent effects for a specific crystallographic site, even when polycrystalline samples are used. The theory and experimental considerations involved in both types of experiments will be outlined and illustrated with examples of work on high T_c superconductors, zeolites, magnetic materials, and mixed valence compounds.