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A long-range-corrected time-dependent density functional theory
Yoshihiro Tawada1, Takao Tsuneda, Susumu Yanagisawa
1Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan.
The Journal of Chemical Physics
|July 23, 2004
Summary
The long-range corrected time-dependent density functional theory (LC-TDDFT) accurately predicts molecular excitation energies and strengths. This method overcomes significant underestimations found in standard TDDFT, improving computational chemistry predictions.
Area of Science:
- Computational Chemistry
- Quantum Mechanics
- Theoretical Physics
Background:
- Time-dependent density functional theory (TDDFT) often underestimates Rydberg and charge-transfer excitation energies.
- Standard TDDFT using pure functionals exhibits significant errors in excitation energies and oscillator strengths.
- Accurate prediction of electronic excitation is crucial for understanding molecular properties and reactions.
Purpose of the Study:
- To evaluate the efficacy of the long-range correction (LC) scheme applied to TDDFT (LC-TDDFT).
- To address the underestimation of Rydberg excitation energies, oscillator strengths, and charge-transfer excitation energies in TDDFT.
- To improve the accuracy of TDDFT calculations for molecular electronic excitations.
Main Methods:
- Application of the long-range correction (LC) scheme to exchange functionals within TDDFT.
- Calculation of vertical excitation energies for typical molecules using LC-TDDFT.
- Comparison of LC-TDDFT results with those obtained from TDDFT employing pure functionals.
Main Results:
- LC-TDDFT yields accurate excitation energies with errors typically within 0.5 eV.
- LC-TDDFT provides reasonable oscillator strengths, significantly improving upon standard TDDFT.
- Standard TDDFT underestimates excitation energies by approximately 1.5 eV and oscillator strengths by two orders of magnitude for Rydberg excitations.
- LC-TDDFT accurately models the charge-transfer excitation energy's asymptotic behavior for long intramolecular distances.
Conclusions:
- The long-range correction scheme substantially enhances the accuracy of TDDFT for electronic excitation calculations.
- LC-TDDFT effectively resolves the underestimation issues prevalent in standard TDDFT, particularly for Rydberg and charge-transfer excitations.
- The improved performance of LC-TDDFT suggests that the lack of long-range orbital-orbital interaction in pure functionals contributes to TDDFT's inaccuracies.