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Spin in density-functional theory

Authors

  • Christoph R. Jacob,

    Corresponding author
    1. Karlsruhe Institute of Technology (KIT), Center for Functional Nanostructures, Wolfgang-Gaede-Straße 1a, 76131 Karlsruhe, Germany
    • Karlsruhe Institute of Technology (KIT), Center for Functional Nanostructures, Wolfgang-Gaede-Straße 1a, 76131 Karlsruhe, Germany
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  • Markus Reiher

    Corresponding author
    1. ETH Zurich, Laboratorium für Physikalische Chemie, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland
    • Karlsruhe Institute of Technology (KIT), Center for Functional Nanostructures, Wolfgang-Gaede-Straße 1a, 76131 Karlsruhe, Germany
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Abstract

The accurate description of open-shell molecules, in particular of transition metal complexes and clusters, is still an important challenge for quantum chemistry. Although density-functional theory (DFT) is widely applied in this area, the sometimes severe limitations of its currently available approximate realizations often preclude its application as a predictive theory. Here, we review the foundations of DFT applied to open-shell systems, both within the nonrelativistic and the relativistic framework. In particular, we provide an in-depth discussion of the exact theory, with a focus on the role of the spin density and possibilities for targeting specific spin states. It turns out that different options exist for setting up Kohn–Sham DFT schemes for open-shell systems, which imply different definitions of the exchange–correlation energy functional and lead to different exact conditions on this functional. Finally, we suggest possible directions for future developments. © 2012 Wiley Periodicals, Inc.

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