Preserving Symmetry and Degeneracy in the Localized Orbital Scaling Correction

Density Functional Theory (DFT) has proven to be an invaluable tool for chemical predictions. However, standard density functional approximations (DFAs) can be inadequate in cases where nearly degenerate orbital energies play a key role such as dissociation energies, reaction barriers, and band gaps. Traditionally, these problems stem from self-interaction error. Recently, they have been identified as arising instead from delocalization error in DFAs, which stems from an incorrect treatment of fractional electron charge. The localized orbital scaling correction (LOSC) was introduced to correct for this error, which greatly improves DFA descriptions of band gaps, photoemission spectra, and dissociation limits of cationic species [1]. However, the original method did not preserve system symmetries and degeneracies. In this talk, we present the newest implementation of LOSC [2] that addresses system symmetry and more robustly preserves system degeneracies. This is mainly accomplished by the localized orbitals produced by the newest version of LOSC, which obey a subset of the system symmetry when allowed.

[1] C. Li, X. Zheng, N. Su, W. Yang, Nat. Sci. Rev., 5(2):203-215, 2018
[2] N. Su, A. Mahler, W. Yang, J. Phys. Chem. Lett., 11(4):1528-1535, 2020