First-principles calculation of the Coulomb interaction parameters U and J for actinide dioxides

We present ab initio calculations of effective interaction parameters U and J for dioxides of actinides from uranium to curium. We first use a self-consistent scheme using DFT + U and constrained random phase approximation (cRPA). For UO2, and NpO2, we find self-consistent values of U and J leading to values of gap in agreement with experiments. For PuO2, the value of U is underestimated. For AmO2 and CmO2, we find very low self-consistent values. We compare projected local orbital Wannier functions to maximally localized Wannier functions and find a weak effect of the localization on interaction parameters. We suggest that spin-orbit coupling, and antiferromagnetism, could improve these results partially. We also extend our calculations by treating the p bands from oxygen as correlated, as in Seth et al. [Phys. Rev. Lett. 119, 056401 (2017)], and show that the results are rather independent of self-consistency in this approach. Comparing these calculations, our conclusion is that including electron interaction on oxygen p orbitals is necessary both to improve the density of states and to compute more meaningful and predictive values of effective interaction parameters.