2022-12-16
非放射性崩壊経路は、光活性分子の励起状態ダイナミクスにおいて重要な役割を果たし、その結果、太陽電池などの光捕集デバイスの効率に影響を与える。
これらの経路の多くはよく理解されており、理論モデルを用いてその速度を予測することができる。しかし、セイムスピン（または非断熱）経路は、システムサイズに関してスケーリングが複雑なため、モデル化が特に困難である。
DFTは以前、非断熱的な行列結合要素や励起状態内の内部変換率の計算に成功した。しかし、同一スピンの非輻射率や交換相関成分に対する様々な密度関数の適用性と精度は未知のままである。
本研究では、モノマーのペリレンクロモフォアをケーススタディとして、非放射性崩壊経路を計算するための密度関数の精度を総合的に調査しました。
RMIT大学とメルボルン大学を拠点とする研究者らは、密度汎関数理論の中で、実験データを高い忠実度で再現できるいくつかの処理を特定することができました。
この結果はJournal of Chemical Theory and Computationに掲載され、こちらでご覧いただけます。
＜関連情報＞
- https://excitonscience.com/news/benchmarking-dft-functionals-non-radiative-decay
- https://pubs.acs.org/doi/abs/10.1021/acs.jctc.2c00888
非励起状態光物理学 I：非断熱結合と内部変換速度定数計算のための密度関数のベンチマーク Interexcited State Photophysics I: Benchmarking Density Functionals for Computing Nonadiabatic Couplings and Internal Conversion Rate Constants
Anjay Manian, Rohan J. Hudso, Pria Ramkissoon, Trevor A. Smith and Salvy P. Russo
Journal of Chemical Theory and Computation Published:December 9, 2022
DOI:https://doi.org/10.1021/acs.jctc.2c00888
Abstract
We present the first benchmarking study of nonadiabatic matrix coupling elements (NACMEs) calculated using different density functionals. Using the S1 → S0 transition in perylene solvated in toluene as a case study, we calculate the photophysical properties and corresponding rate constants for a variety of density functionals from each rung of Jacob’s ladder. The singlet photoluminescence quantum yield (sPLQY) is taken as a measure of accuracy, measured experimentally here as 0.955. Important quantum chemical parameters such as geometries, absorption, emission, and adiabatic energies, NACMEs, Hessians, and transition dipole moments were calculated for each density functional basis set combination (data set) using density functional theory based multireference configuration interaction (DFT/MRCI) and compared to experiment where possible. We were able to derive simple relations between the TDDFT and DFT/MRCI photophysical properties; with semiempirical damping factors of ∼0.843 ± 0.017 and ∼0.954 ± 0.064 for TDDFT transition dipole moments and energies to DFT/MRCI level approximations, respectively. NACMEs were dominated by out-of-plane derivative components belonging to the center-most ring atoms with weaker contributions from perturbations along the transverse and longitudinal axes. Calculated theoretical spectra compared well to both experiment and literature, with fluorescence lifetimes between 7.1 and 12.5 ns, agreeing within a factor of 2 with experiment. Internal conversion (IC) rates were then calculated and were found to vary wildly between 106–1016 s–1 compared with an experimental rate of the order 107 s–1. Following further testing by mixing data sets, we found a strong dependence on the method used to obtain the Hessian. The 5 characterized data sets ranked in order of most promising are PBE0/def2-TZVP, ωB97XD/def2-TZVP, HCTH407/TZVP, PBE/TZVP, and PBE/def2-TZVP.
