Capturing Strong Electron Correlation with Partition-DFT

Standard approximations for the exchange-correlation (XC) functional in Kohn-Sham-DFT (KS-DFT) typically lead to unacceptably large errors when applied to strongly-correlated electron systems. Partition-DFT is a formally exact reformulation of KS-DFT in which the ground-state density and energy of a system are obtained through self-consistent calculations on isolated fragments. Here we show how the typical errors of the standard approximations in KS-DFT can be largely avoided through Partition-DFT even when the same approximations are applied to the fragments. Our method is illustrated with Partition-DFT calculations on simple models of "strongly-correlated" hydrogen chains, for which numerically exact results are available through the Density Matrix Renormalization Group (DMRG). With a suitable "overlap approximation" (OA) for the partition energy, the binding curves of the hydrogen chains are significantly improved. We are exploring whether the OA also yields the correct power-law decay of the density dimerization orders observed in stretched hydrogen chains.