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Density Driven Correlations in Ensemble Density Functional Theory: Insights from Simple Excitations in Atoms

preprint
submitted on 07.10.2019 and posted on 11.10.2019 by Tim Gould, Stefano Pittalis
Ensemble density functional theory extends the usual Kohn-Sham machinery to quantum state ensembles involving ground- and excited states. Recent work by the authors [Phys. Rev. Lett. 119, 243001 (2017); 123, 016401 (2019)] has shown that both the Hartree-exchange and correlation energies can attain unusual features in ensembles. Density-driven (DD) correlations -- which account for the fact that pure-state densities in Kohn-Sham ensembles do not necessarily reproduce those of interacting pure states -- are one such feature. Here we study atoms (specifically S--P and S--S transitions) and show that the magnitude and behaviour of DD correlations can vary greatly with the variation of the orbital angular momentum of the involved states. Such estimations are obtained through an approximation for DD correlations built from relevant exact conditions and plausible assumptions for weakly correlated systems.

History

Email Address of Submitting Author

t.gould@griffith.edu.au

Institution

Griffith University

Country

Australia

ORCID For Submitting Author

0000-0002-7191-9124

Declaration of Conflict of Interest

No conflict of interest

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