Charge localization in mixed-valence uranium oxides from diffraction anomalous fine structure (DAFS)

In the uranium-oxygen system an interesting interplay between the uranium charge distribution and crystallographic properties exists. The application of diffraction techniques allows to resolve the structural elements, whereas the assessment of chemical states is usually performed from spectroscopic methods, separate from each other. Ambiguity sometimes remains on the actual charge localization, especially in complex molecules. We propose to perform DAFS around the U L3-edge (17.170 keV) on mixed-valence uranium oxides, in order to obtain site-specific information on the chemical state of uranium. These type of experiments, further supported by Density Functional Theory calculations, can provide a unique and unprecedented insight on the charge localization in uranium compounds, which is invaluable information with respect to nuclear fuel material properties.