Proper alignment of Fermi Level in a Tri-anionic Molecule

Descriptions of anionic molecules, within approximations to density-functional theory, has been problematic due to self-interaction error which pushes the eigenvalues to higher energy and creates non-systematic errors in Fermi levels. A new approach for improving the Perdew-Zunger self-interaction[A], referred to as the Fermi-Löwdin orbital-based self-interaction correction (FLO-SIC), is introduced to treat a tri-anionic system. The Fermi–Löwdin orbitals are localized but due to the fact they are constructed directly from the spin-density matrices, they lead to a set of orbitals that have the property that each and every orbital is explicitly invariant to unitary transformations which leads to a unitarily invariant and size-extensive expression for the energy. The improvement of alignment of Fermi level in the system is demonstrated and related isotope fractionation is reported. Zero-point splittings will also be presented and the impact of self-interaction correction will be discussed.
[A] Pederson et al., JCP, 140, 121103 (2014)