Nearly degenerate excitations in density functional theory
Abstract
Excited state properties can be calculated in density functional theory (DFT) via different approaches. Second-order Goerling-Levy perturbation theory can be applied to both non-degenerate and degenerate states. Some excitations are shown to be poorly described to first order (i.e. in exact exchange), no matter how weakly correlated the system is. Time-dependent DFT(TDDFT) with linear response also yields excitations, but only single excitations within the (standard) adiabatic approximation. A frequency-dependent exchange-correlation kernel is needed to capture double excitations. Results are demonstrated on a simple model and short chain polyenes.
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARH38010Z