Weight dependence of local exchange-correlation functionals in ensemble density-functional theory: Double excitations in two-electron systems

Clotilde Marut, Bruno Senjean, Emmanuel Fromager, Pierre François Loos*

*Corresponding author for this work

    Research output: Contribution to JournalArticleAcademicpeer-review

    Abstract

    Gross-Oliveira-Kohn (GOK) ensemble density-functional theory (GOK-DFT) is a time-independent extension of density-functional theory (DFT) which allows the computation of excited-state energies via the derivatives of the ensemble energy with respect to the ensemble weights. Contrary to the time-dependent version of DFT (TD-DFT), double excitations can be easily computed within GOK-DFT. However, to take full advantage of this formalism, one must have access to a weight-dependent exchange-correlation functional in order to model the infamous ensemble derivative contribution to the excitation energies. In the present article, we discuss the construction of first-rung (i.e., local) weight-dependent exchange-correlation density-functional approximations for two-electron atomic and molecular systems (He and H2) specifically designed for the computation of double excitations within GOK-DFT. In the spirit of optimally-tuned range-separated hybrid functionals, a two-step system-dependent procedure is proposed to obtain accurate energies associated with double excitations.

    Original languageEnglish
    Pages (from-to)402-423
    Number of pages22
    JournalFaraday Discussions
    Volume224
    Early online date15 Jun 2020
    DOIs
    Publication statusPublished - 1 Dec 2020

    Funding

    PFL thanks Radovan Bast and Anthony Scemama for technical assistance, as well as Julien Toulouse for stimulating discussions on double excitations. CM thanks the UniversitéPaul Sabatier (Toulouse, France) for a PhD scholarship. This work has also been supported through the EUR grant NanoX ANR-17-EURE-0009 in the framework of the “Programme des Investissements d’Avenir”.

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