Insight into ThO2 electronic structure through the O K edge XANES

Ligand K-edge XANES is an effective mean to probe the electronic structure of actinides in molecular complexes and solid-state compounds. The hybridization of actinide 5f and 6d states with ligand p-orbitals makes the metal contribution visible in the K-edge XANES, offering a different point of view to observe the electronic structure of the system.

In this contribution, we will report our recent analysis of the O K-edge XANES of ThO2 and compare it with that of CeO2 [1]. We found that despite the similarity of the spectra, the interpretation of the main spectral features is different and reflects the different roles of f- and d- orbitals in shaping the electronic structure of the two compounds.
The stronger localization of Ce 4f over Th 5f emerges from the sharpness of the corresponding spectral features. The splitting of the 5d/6d orbitals in two bands, i.e., eg and t2g, is observed and reproduced by DFT-bases calculations. The Ce 4f orbitals are found below the 5d bands, while for ThO2 the 5f band is between the 6d-eg and 6d-t2g bands. Figure 1 summarizes these findings.