Suppressing exchange-correlation errors through a Generalized Overlap Approximation in Partition-DFT

Quantum embedding methods can in principle lead to linear scaling and multilevel-accuracy calculations of electronic properties of molecules and materials. Partition Density Function Theory (P-DFT), a density-based embedding method, features a unique interaction potential and in many cases fragments with fractional numbers of electrons. An "overlap approximation" (OA) for the partition energy of P-DFT has been shown to eliminate errors caused by the underlying exchange-correlation approximations, such as delocalization and static-correlation errors, even when using the Local Density Approximation for the fragments. Although the initial formulation of the OA was applicable only to small homonuclear diatomic molecules, we have revised its derivation and demonstrated its applicability to larger, less symmetric systems.