Strongly correlated systems are a massive challenge to electronic structure methods including Density Functional Theory (DFT). Single-particle methods such as Hartree-Fock, B3LYP and other approximate functionals in DFT, miss the key movements of electrons in these systems.In this talk we investigate some of the dramatic failures observed in small systems that capture the essence of the problem. As an example of the complexity of the electronic structure, we will see clearly the challenges for approximate functionals in DFT to describe some of the simple movements of electrons. A clear manifestation is the complete failure of all functionals in the literature to give the energy of both infinitely stretched H2+ and infinitely stretched H2. More examples in chemistry and physics will be shown, ranging from the behaviour of electrons in the simplest chemical reactions to the gap of the 1D-Hubbard model and electron transport.Overall strongly correlated systems offer one of the grand challenges of the exchange-correlation functional: it is the same energy expression that has to be exact for all systems. This encompasses normal chemistry and also the interesting cases where an underlying change in the Hamiltonian is smooth but the chemical change is discontinuous. This is a great challenge for Exc[?] that must be considered in the development of new functionals.

Density functional view of strongly correlated electronic structure

248th National Meeting (2014)

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