Effect of ensemble generalization on the highest-occupied Kohn-Sham eigenvalue

Abstract

There are several approximations to the exchange-correlation functional in density-functional theory that accurately predict total energy-related properties of many-electron systems, such as binding energies, bond lengths, and crystal structures. Other approximations are designed to describe potential-related processes, such as charge transfer and photoemission. However, the development of a functional which can serve the two purposes simultaneously is a long-standing challenge. Trying to address it, we employ in the current work the ensemble generalization procedure proposed in Phys. Rev. Lett. 110, 126403 (2013). Focusing on the prediction of the ionization potential via the highest occupied Kohn-Sham eigenvalue, we examine a variety of exchange-correlation approximations: the local spin-density approximation, semi-local generalized gradient approximations, and global and local hybrid functionals. Results for a test set of 26 diatomic molecules and single atoms are presented. We find that the aforementioned ensemble generalization systematically improves the prediction of the ionization potential, for various systems and exchange-correlation functionals, without compromising the accuracy of total energy-related properties. We specifically examine hybrid functionals. These depend on a parameter controlling the ratio of semi-local to non-local functional components. The ionization potential obtained with ensemble-generalized functionals is found to depend only weakly on the parameter value, contrary to common experience with non-generalized hybrids, thus eliminating one aspect of the so-called `parameter dilemma' of hybrid functionals.

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Cited by in corpus (9)

• The Importance of being consistent
• How is the derivative discontinuity related to steps in the exact Kohn-Sham potential?
• Ensemble Density Functional Theory of Neutral and Charged Excitations
• Effect of ensemble generalization on the highest-occupied Kohn-Sham eigenvalue
• Learning the energy curvature versus particle number in approximate density functionals
• Approximations to the exact exchange potential: KLI versus semilocal
• Variations of the Hartree-Fock fractional-spin error for one electron
• Ionization Potentials and Fundamental Gaps in Atomic Systems from the Ensemble-DFT Approach
• Review of the finite difference Hartree-Fock method for atoms and diatomic molecules, and its implementation in the x2dhf program