Overcoming delocalization and static correlation errors and describing photoemission and optical excitation with ground state DFT calculations

We will report our development of the localized orbital scaling correction (LOSC) in overcoming systematic delocalization and static correlation errors and development of DFT for describing photoemission and optical excitation with ground state DFT calculations. LOSC is capable of correcting system energy, energy derivative and electron density in a size-consistent manner for all commonly used density functional approximations (DFAs). The LOSC and fractional spin LOSC lead to systematically improved results, including the dissociation of ionic species, single bonds, multiple bonds without breaking the space or spin symmetry, the band gaps of molecules and polymer chains, the energy and density changes upon electron addition and removal, and photoemission spectra, and energy-level alignments for interfaces. The LOSC DFA orbital energies are excellent approximations to quasiparticle energies, comparable to or better than GW. This also leads to the QE-DFT (quasiparticle energies from DFT) approach: the calculations of excitation energies of the N-electron systems from the ground state DFA calculations of the (N - 1)-electron systems. Results show good performance with accuracy similar to TDDFT for valence excitations with commonly used DFAs with or without LOSC. For charge transfer and Rydberg states, good accuracy was obtained only with the use of LOSC DFA. The QE-DFT method has been further developed to describe excited-state potential energy surfaces (PESs), conical intersections, and the analytical gradients of excited-state PESs. We have also made the LOSC software available for the community.