Systematically Improvable Generalization of Self-Interaction Corrected Density Functional Theory

Perdew-Zunger self-interaction correction (PZSIC) reintroduces an exact constraint to approximate density functional theory (DFT), but can paradoxically degrade performance and is not systematically improvable. We use the Adiabatic Projection formalism to derive PZSIC in terms of a reference system experiencing only electron self-interaction. Generalization introduces correlation into the reference system, systematically bridging from PZSIC to exact wavefunction theory. Minimal active spaces resolve the PZSIC paradox, accurately treating near-equilibrium and strongly-correlated systems.