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arXiv · 2001.08605

Individual correlations in ensemble density-functional theory: State-driven/density-driven decompositions without additional Kohn-Sham systems

Emmanuel Fromager
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Abstract

Gould and Pittalis [Phys. Rev. Lett. 123, 016401 (2019)] recently revealed a density-driven (DD) correlation energy that is specific to many-electron ensembles and must be accounted for by approximations. We derive in this Letter a general and simpler expression in terms of the ensemble weights, the ensemble Kohn-Sham (KS) orbitals, and their linear response to variations in the ensemble weights. As no additional state-driven KS systems are needed, its evaluation is greatly simplified. We confirm the importance of DD effects and introduce a direct and promising route to approximations.

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Emmanuel Fromager. 2020-05-27. Individual correlations in ensemble density-functional theory: State-driven/density-driven decompositions without additional Kohn-Sham systems. https://doi.org/10.1103/physrevlett.124.243001

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