Electronic and mechanical properties of ordered (Pu, U) O2 compounds: A density functional theory +U study

We have systematically studied the electronic and mechanical properties of the ordered binary PuxU1−xO2 compounds with x = 0.25, 0.5, and 0.75. It is found that both in antiferromagnetic and ferromagnetic states, the lattice constants and computed total energies of the mixed oxides (MOXs) obey the linear Vegard’s law. Through electronic structure calculations, we reveal that the uranium and plutonium 5f electrons states do not overlap with each other, resulting in much smaller energy band gaps for MOX than UO2 and PuO2. At the mechanical side, our calculations indicate that all PuxU1−xO2 compounds satisfy the mechanical stability criteria, and the elastic constants and moduli of MOX are similar to that of UO2 and PuO2. The obtained Poisson’s ratio for Pux U1−xO2 compounds is in good agreement with experimental results.