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

TL;DR

This paper introduces a modified LDA+U method that corrects self-interaction errors in DFT calculations of f-electron systems, accurately predicting orbital ground states and degeneracies in lanthanide and actinide compounds.

Contribution

A novel nonspherical self-interaction correction in LDA+U that improves the accuracy of orbital ground state predictions in f-electron systems.

Findings

Reproduces expected degeneracy of f^1 and f^2 states in free ions.

Correctly predicts ground states in solid PrO2.

Potentially useful for studying f- and heavy-d elements.

Abstract

The electronic structure of lanthanide and actinide compounds is often characterized by orbital ordering of localized $f$-electrons. Density-functional theory (DFT) studies of such systems using the currently available 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 $f^2$ states in free ions and the correct ground states in solid PrO$_2$. We expect our method to be useful in studying compounds of $f$- and heavy-$d$ elements.