Interexcited State Photophysics I: Benchmarking Density Functionals for Computing Nonadiabatic Couplings and Internal...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Photophysics

Background:

• Accurate calculation of nonadiabatic matrix coupling elements (NACMEs) is crucial for understanding photophysical processes.
• Density functional theory (DFT) methods offer a computationally efficient route to these properties, but their accuracy varies.
• Benchmarking different DFT functionals is essential for reliable predictions of molecular excited-state dynamics.

Purpose of the Study:

• To conduct the first benchmarking study of NACMEs calculated using various density functionals.
• To evaluate the accuracy of different DFT functionals for predicting photophysical properties of perylene in its S1 state.
• To identify the most reliable DFT methods for future studies of excited-state dynamics.

Main Methods:

• Calculated NACMEs, photophysical properties, and related quantum chemical parameters for perylene using multiple density functionals.
• Employed density functional theory based multireference configuration interaction (DFT/MRCI) for calculations.
• Compared theoretical results with experimental data, including singlet photoluminescence quantum yield (sPLQY) and fluorescence lifetimes.

Main Results:

• Derived simple relations between time-dependent DFT (TDDFT) and DFT/MRCI photophysical properties.
• NACMEs were primarily influenced by out-of-plane derivative components.
• Calculated internal conversion (IC) rates showed significant variation, highlighting the sensitivity to the chosen DFT method.

Conclusions:

• The study identified PBE0/def2-TZVP and ωB97XD/def2-TZVP as the most promising DFT methods for calculating NACMEs and photophysical properties.
• The choice of method for calculating the Hessian significantly impacts the accuracy of the results.
• This work provides a foundation for selecting appropriate DFT functionals in excited-state calculations.