X-ray Absorption Near-Edge Structure of the Actinide Dioxide Series (ThO₂ – BkO₂): A DFT + <i>U</i> Study

We have systematically studied the X-ray absorption near-edge structure (XANES) of the actinide dioxide series (AnO2, An = Th – Bk), performing simulations at the An L3, An M4, and O K edges. A periodic bulk model and the DFT + U method are employed for these simulations. Parameters, such as broadening factors and core-hole (CH) size and position, are chosen based on comparisons with experimental spectra. The ground states provide accurate predictions for the An L3 edges, which are nearly identical across all An. The impact of the CH on the An M4 edge simulations depends on the system, and a comparison across the An series shows a clear extension of the peaks to lower energies for the An M4 edge. The CH is crucial for the accurate prediction of the O K edge, and extension of peaks to lower energies also shows in the pre-edge region of the O K edge along the An series.