Local Hartree–Fock orbitals using a three-level optimization strategy for the energy

Authors

  • Ida-Marie Høyvik,

    Corresponding author
    1. Department of Chemistry, qLEAP Center for Theoretical Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus, Denmark
    • Department of Chemistry, qLEAP Center for Theoretical Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus, Denmark
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  • Branislav Jansik,

    1. VSB-TUO, 17. listopadu 15/2172, 798 33 Ostrava – Poruba, Czech Republic
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  • Kasper Kristensen,

    1. Department of Chemistry, qLEAP Center for Theoretical Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus, Denmark
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  • Poul Jørgensen

    1. Department of Chemistry, qLEAP Center for Theoretical Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus, Denmark
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Abstract

Using the three-level energy optimization procedure combined with a refined version of the least-change strategy for the orbitals—where an explicit localization is performed at the valence basis level—it is shown how to more efficiently determine a set of local Hartree–Fock orbitals. Further, a core–valence separation of the least-change occupied orbital space is introduced. Numerical results comparing valence basis localized orbitals and canonical molecular orbitals as starting guesses for the full basis localization are presented. The results show that the localization of the occupied orbitals may be performed at a small computational cost if valence basis localized orbitals are used as a starting guess. For the unoccupied space, about half the number of iterations are required if valence localized orbitals are used as a starting guess compared to a canonical set of unoccupied Hartree–Fock orbitals. Different local minima may be obtained when different starting guesses are used. However, the different minima all correspond to orbitals with approximately the same locality. © 2013 Wiley Periodicals, Inc.

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