Electronic structure of mononuclear Cu-based molecule from density-functional theory with self-interaction correction

We investigate the electronic structure of a planar mononuclear Cu-based molecule [Cu(C6H4S2)2]z in two oxidation states (z = −2, −1) using density-functional theory (DFT) with Fermi–Löwdin orbital (FLO) self-interaction correction (SIC). The dianionic was proposed to be promising qubit candidate. Self-interaction error within approximate DFT functionals renders severe delocalization electron and spin densities arising from 3d orbitals. FLO-SIC method relies on optimization descriptors (FODs) which localized occupied orbitals are constructed create SIC potentials. Starting many initial sets FODs, we employ frozen-density loop algorithm study molecule. find that remains unchanged despite somewhat different final FOD configurations. In state (spin S 1/2), density originates Cu d p an ratio 2:1, quantitative agreement multireference calculations, while case SIC-free DFT, is reversed. Overall, lowers energies and, particular, unhybridized ligands significantly, substantially increases energy gap between highest molecular (HOMO) lowest unoccupied (LUMO) compared results. HOMO–LUMO larger than monoanionic state, consistent experiment. Our results suggest positive outlook description magnetic exchange coupling 3d-element-based systems.