## Delocalization and Static Correlation in Partition Density-Functional Theory    [PDF]

Approximate exchange-correlation functionals in Kohn-Sham (KS) density-functional theory (DFT) struggle to describe the delocalization and static correlation of electrons. This leads to poor dissociation energies, which are either vastly underestimated when delocalization is present or vastly overestimated when static correlation is present. We demonstrate how the alternative framework of partition density-functional theory (PDFT) can correctly describe bond dissociation through its focus on, and correct treatment of, sharply-defined `atoms-in-molecules'. This method is illustrated through calculations on the dissociation of H$_2^+$ and H$_2$, the two paradigm systems displaying delocalization and static correlation. For the case of stretched H$_2$, we show that our proposed method leads to an effective KS potential which contains a peak around the bond midpoint. This feature is absent from almost all density-functional approximations but has been shown to appear in the {\em exact} KS potential and is essential for the correct description of electron dynamics.