title: Exact Kohn-Sham versus Hartree-Fock in momentum space: Examples of two-fermion systems.
abstract: The question of how density functional theory (DFT) compares with Hartree-Fock (HF) for the computation of momentum-space properties is addressed in relation to systems for which (near) exact Kohn-Sham (KS) and HF one-electron matrices are known. This makes it possible to objectively compare HF and exact KS and hence to assess the potential of DFT for momentum-space studies. The systems considered are the Moshinsky [Am. J. Phys. 36, 52 (1968)] atom, Hooke's atom, and light two-electron ions, for which expressions for correlated density matrices or momentum densities have been derived in closed form. The results obtained show that it is necessary to make a distinction between true and approximate DFTs.
authors.affiliation: Laboratoire Structure, Propriété et Modélisation des Solides (CNRS, Unité Mixte de Recherche 85-80), Ecole Centrale Paris, Grande Voie des Vignes, 92295 Chatenay-Malabry, France. at_home@club-internet.fr
authors.forename: Sébastien
authors.initials: S
authors.lastname: Ragot