Obtaining correct orbital ground states in f-electron systems using a nonspherical self-interaction-corrected LDA plus 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 (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 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 PrO2. We expect our method to be useful in studying electronic excitations and entropies in f and heavy-d elements.