Yu, S.-W., Tobin, J. G., Crowhurst, J. C., Sharma, S., Dewhurst, J. K., Olalde Velasco, P., Lang, W. L., Siekhaus, W. J.
f - f origin of the insulating state in uranium dioxide: X-ray absorption experiments and first-principles calculations
Physical Review B 83, (16),pp 165102/1-8 (2011)
We have performed x-ray absorption experiments on uranium dioxide (UO2) at the O 1s, U 4d, U 4f, and U 5d edges. After comprehensive energy calibrations for O 1s, U 4d, and U 4f spectra, we have used the U 4d and 4f spectra to sort the energetic positions of the 5f and the 6d states in the unoccupied band unambiguously. This demonstrates conclusively that UO2 is an f - f Mott-Hubbard insulator, where the electronic repulsion between f electrons is responsible for the insulating state. Calculations performed within the U-corrected generalized gradient approximation of the optical response of UO2 permit direct comparison with the absorption spectra and confirm the experimental results.
TH-2011-25