Second-order perturbative correlation energy functional in the ensemble density-functional theory

@article{Yang2021SecondorderPC,
  title={Second-order perturbative correlation energy functional in the ensemble density-functional theory},
  author={Zeng-Hui Yang},
  journal={Physical Review A},
  year={2021}
}
We derive the second-order approximation (PT2) to the ensemble correlation energy functional by applying the Görling-Levy perturbation theory on the ensemble density-functional theory (EDFT). Its performance is checked by calculating excitation energies with the direct ensemble correction method in 1D model systems and 3D atoms using numerically exact Kohn-Sham orbitals and potentials. Comparing with the exchange-only approximation, the inclusion of the ensemble PT2 correlation improves the… Expand

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