Exploring the Thermal and Electronic Behavior of Actinide Oxides: A Combined DFT and XAFS Study of UO₂ and PuO₂

The electronic structure and thermal behavior of uranium dioxide (UO₂) and plutonium dioxide (PuO₂), two critical actinide oxides with significant applications in contemporary technology and nuclear energy, are investigated in the present study. Density Functional Theory (DFT) and X-ray Absorption Fine Structure (XAFS) spectroscopy are used in conjunction to examine how their electronic and structural properties change with temperature. DFT calculations are used to elucidate the band structures and density of states (DOS) of UO₂ and PuO₂, highlighting the importance of strong electron interactions in their 5f orbitals. XAFS calculations, which are carried out using the FEFF8.2 code, provide insight into the local atomic environment and thermal stability of these materials. The results demonstrated that UO₂ is more thermally stable than PuO₂ and exhibits less structural degradation up to 1000 K. However, PuO₂ reacts more strongly to heat excitation, showing larger atomic displacements and reduced scattering intensity. These findings demonstrate the importance of understanding the interplay between electronic structure, lattice dynamics, and thermal stability in actinide oxides, which is crucial for their application in demanding environments such as nuclear reactors and high-temperature electronics.