Direct extraction of excitation energies from ensemble density-functional theory

Abstract

A very specific ensemble of ground and excited states is shown to yield an exact formula for any excitation energy as a simple correction to the energy difference between orbitals of the Kohn-Sham ground state. This alternative scheme avoids either the need to calculate many unoccupied levels as in time-dependent density functional theory (TDDFT) or the need for many self-consistent ensemble calculations. The symmetry-eigenstate Hartree-exchange (SEHX) approximation yields results comparable to standard TDDFT for atoms. With this formalism, SEHX yields approximate double-excitations, which are missed by adiabatic TDDFT.

6 pages, 2 figures

References in corpus (2)

• Understanding Band Gaps of Solids in Generalized Kohn-Sham Theory
• Exact ensemble density functional theory for excited states in a model system: investigating the weight dependence of the correlation energy

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