Obtaining correct orbital ground states in f -electron systems using a nonspherical self-interaction-corrected LDA + U method

The electronic structure of lanthanide and actinide compounds is often characterized by orbital ordering of localized $f$ electrons. Density-functional theory studies of such systems using the currently available local-density approximation $(\text{LDA})+U$ method are plagued by significant orbital-dependent self-interaction, leading to erroneous orbital ground states. An alternative scheme that modifies the exchange, not Hartree, energy is proposed as a remedy. We show that our $\text{LDA}+U$ approach reproduces the expected degeneracy of ${f}^{1}$ and certain ${f}^{2}$ states in free ions and the correct ground states in solid ${\text{PrO}}_{2}$. We expect our method to be useful in studying electronic excitations and entropies in $f$ and heavy-$d$ elements.