Electron Spin Densities in Open-Shell Polycyclic Aromatic Hydrocarbons by Self-Interaction-Corrected Density Functional Approximations

Electron spin densities in open-shell systems such as polycyclic aromatic hydrocarbons are studied using recent locally scaled self-interaction-correction (LSIC) (Zope et. al. Phys. Chem. Chem. Phys., 2021, 23, 2406-2418) method and the Perdew-Zunger SIC (PZSIC) method within the FLOSIC scheme. Descriptions of such systems are usually challenging for density functional approximations due to pronounced electron delocalization and spin polarization effects because of the planarity of their structure and electron conjugation. Spin densities calculated are compared against benchmark QCISD results. Results show that PZSIC tends to overcorrect the density delocalization tendency of LSDA and PBE-GGA. On the other hand, the LSIC method with the simplest LSDA functional gives a more balanced description of spin densities resulting in better agreement with benchmark QCISD results.