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Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
Double excitations in finite systems
P Romaniello1, D Sangalli, J A Berger
1Laboratoire des Solides Irradies UMR 7642, CNRS-CEA/DSM, Ecole Polytechnique, F-91128 Palaiseau, France. pina.romaniello@polytechnique.edu
The Journal of Chemical Physics
|February 5, 2009
Summary
We introduce a frequency-dependent kernel for time-dependent density-functional theory (TDDFT) to accurately describe double-excitation states in molecules. This approach overcomes limitations of static kernels, improving excited-state calculations.
Area of Science:
- Quantum Chemistry
- Computational Physics
- Theoretical Chemistry
Background:
- Time-dependent density-functional theory (TDDFT) is a standard method for calculating electronic properties.
- Standard TDDFT approximations struggle to describe excited states with double- and higher-excitation character, especially in open-shell systems.
- Existing methods often yield excitation energies with only single-excitation character.
Purpose of the Study:
- To develop a novel frequency-dependent exchange-correlation (xc) kernel for TDDFT.
- To enable the accurate description of double-excitation states within TDDFT for finite systems.
- To improve the calculation of excited-state properties, particularly for challenging molecular systems.
Main Methods:
- Development of a frequency-dependent xc kernel derived from the Bethe-Salpeter equation.
- Inclusion of a dynamically screened Coulomb interaction W(omega).
- Application to a two-electron model system to validate the approach.
Main Results:
- The proposed frequency-dependent xc kernel successfully reproduces double excitations in TDDFT calculations.
- This method overcomes the limitations of static approximations, which fail to capture double-excitation character.
- The frequency dependence of the screened Coulomb interaction is crucial for describing these states.
Conclusions:
- The novel frequency-dependent xc kernel offers a significant advancement for TDDFT.
- This approach enhances the capability of TDDFT to model complex excited states.
- Accurate calculation of double excitations is now feasible for finite systems using this method.
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