| Autor: |
Stojanović L; Aix Marseille Univ , CNRS, ICR, Marseille, France., Aziz SG; Chemistry Department, Faculty of Science, King Abdulaziz University , Jeddah B.O. 208203, Saudi Arabia., Hilal RH; Chemistry Department, Faculty of Science, King Abdulaziz University , Jeddah B.O. 208203, Saudi Arabia.; Chemistry Department, Faculty of Science, Cairo University , Giza, Egypt., Plasser F; Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna , Währinger Straße 17, 1090 Vienna, Austria., Niehaus TA; Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Lyon, France., Barbatti M; Aix Marseille Univ , CNRS, ICR, Marseille, France. |
| Abstrakt: |
We implemented a version of the decoherence-corrected fewest switches surface hopping based on linear-response time-dependent density functional tight binding (TD-DFTB), enhanced by transition density analysis. The method has been tested for the gas-phase relaxation dynamics of two cycloparaphenylene molecules, [8]CPP and [10]CPP, explaining some important features of their nonadiabatic dynamics, such as the origin of their long fluorescence lifetimes (related to the slow radiative emission from the S 1 state) and the trend of increasing the fluorescence rate with the molecular size (related to an increase in the S 1 -S 0 energy gaps and oscillator strengths in the larger molecule). The quality of the TD-DFTB electronic structure information was assessed through four quantities: excitation energies; charge-transfer (CT) numbers, which estimate the charge transfer character of states; participation ratio (PR), which describes delocalization of electronic density; and participation ratio of natural transition orbitals (PRNTO), which describes the multiconfigurational character of states. These quantities were computed during dynamics and recomputed for the same geometries with the higher-level long-range-corrected TD-LC-DFTB and a lower-level single-determinant approximation for the excited states, SD-(LC)-DFTB. Taking TD-LC-DFTB as the standard, TD-DFTB underestimates the excitation energies by ∼0.5 eV and overestimates CT and PR. SD-DFTB underestimates excitation energies and overestimates CT to the same extent that TD-DFTB does, but it predicts reasonable PR distributions. SD-LC-DFTB leads to an extreme overestimation of the excitation energies by ∼3 eV, overestimates the charge transfer character of the state, but predicts the PR values very close to those obtained with TD-LC-DFTB. |
