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.

Automated summary

In this study, ab initio calculations were performed to determine the effective interaction parameters for actinide dioxides, showing the importance of self-consistent values for aligning with experimental results. Additionally, considering the oxygen p bands as correlated was found to have an impact on the outcomes.