2134/32237
Ljiljana Stojanovic
Ljiljana
Stojanovic
Saadullah G. Aziz
Saadullah G.
Aziz
Rifaat H. Hilal
Rifaat H.
Hilal
Felix Plasser
Felix
Plasser
Thomas A. Niehaus
Thomas A.
Niehaus
Mario Barbatti
Mario
Barbatti
Nonadiabatic dynamics of cycloparaphenylenes with TD-DFTB surface hopping
Loughborough University
2018
untagged
Chemical Sciences not elsewhere classified
Computer Software
2018-03-16 13:41:02
Journal contribution
https://repository.lboro.ac.uk/articles/journal_contribution/Nonadiabatic_dynamics_of_cycloparaphenylenes_with_TD-DFTB_surface_hopping/9390557
© 2017 American Chemical Society. 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.