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Updated: Feb 25, 2026

Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
Direct Extraction of Excitation Energies from Ensemble Density-Functional Theory
Zeng-Hui Yang1, Aurora Pribram-Jones2,3, Kieron Burke4
1Microsystem and Terahertz Research Center, China Academy of Engineering Physics, Chengdu 610200, China.
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.
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