Abstract
We study the structural, magnetic, electronic, thermodynamic and elastic properties of PuC and PuC(0.75)O(0.25) using density-functional theory (DFT) and DFT + U. The nonmagnetic (NM), ferromagnetic (FM) and antiferromagnetic (AFM) configurations are considered in this work. Total energy results obtained with DFT + U indicate that PuC(0.75)O(0.25) has an AFM ground state, matching the AFM nature of stoichiometric PuC. Calculated electronic properties reveal a new density of states peak in PuC(0.75)O(0.25), a consequence of C/O substitution in PuC. Thermodynamically, PuC(0.75)O(0.25) exhibits higher enthalpy difference (H (T) -H (298)), entropy difference (S (T) -S (298)) and heat capacity (C (v) and C (p)) than PuC at the same temperature; elastically, it is predicted to be harder, owing to the stronger ionic character of Pu-O versus Pu-C bonds. Crucially, the formation energy of the oxygen-substitution defect is calculated to be highly spontaneous (-5.11 eV), revealing the fundamental driving force for the oxidation and chemical aging of PuC. These results are intended to provide a valuable reference for further theoretical and experimental investigations of PuC and PuC(0.75)O(0.25).