TY - INPR A1 - Humeniuk, Alexander A1 - Bužančić, Margarita A1 - Hoche, Joscha A1 - Cerezo, Javier A1 - Mitric, Roland A1 - Santoro, Fabrizio A1 - Bonačić-Koutecky, Vlasta T1 - Predicting fluorescence quantum yields for molecules in solution: A critical assessment of the harmonic approximation and the choice of the lineshape function T2 - The Journal of Chemical Physics N2 - For the rational design of new fluorophores, reliable predictions of fluorescence quantum yields from first principles would be of great help. However, efficient computational approaches for predicting transition rates usually assume that the vibrational structure is harmonic. While the harmonic approximation has been used successfully to predict vibrationally resolved spectra and radiative rates, its reliability for non-radiative rates is much more questionable. Since non-adiabatic transitions convert large amounts of electronic energy into vibrational energy, the highly excited final vibrational states deviate greatly from harmonic oscillator eigenfunctions. We employ a time-dependent formalism to compute radiative and non-radiative rates for transitions and study the dependence on model parameters. For several coumarin dyes we compare different adiabatic and vertical harmonic models (AS, ASF, AH, VG, VGF, VH), in order to dissect the importance of displacements, frequency changes and Duschinsky rotations. In addition we analyze the effect of different broadening functions (Gaussian, Lorentzian or Voigt). Moreover, to assess the qualitative influence of anharmonicity on the internal conversion rate, we develop a simplified anharmonic model. We adress the reliability of these models considering the potential errors introduced by the harmonic approximation and the phenomenological width of the broadening function. KW - fluorescence quantum yield Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-199305 UR - https://doi.org/10.1063/1.5143212 N1 - Accepted Manuscript. N1 - This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in A. Humeniuk et al. J. Chem. Phys. 152, 054107 (2020); https://doi.org/10.1063/1.5143212 and may be found at https://doi.org/10.1063/1.5143212. ER - TY - INPR A1 - Titov, Evgenii A1 - Humeniuk, Alexander A1 - Mitric, Roland T1 - Comparison of moving and fixed basis sets for nonadiabatic quantum dynamics at conical intersections T2 - Chemical Physics N2 - We assess the performance of two different types of basis sets for nonadiabatic quantum dynamics at conical intersections. The basis sets of both types are generated using Ehrenfest trajectories of nuclear coherent states. These trajectories can either serve as a moving (time-dependent) basis or be employed to sample a fixed (time-independent) basis. We demonstrate on the example of two-state two-dimensional and three-state five-dimensional models that both basis set types can yield highly accurate results for population transfer at intersections, as compared with reference quantum dynamics. The details of wave packet evolutions are discussed for the case of the two-dimensional model. The fixed basis is found to be superior to the moving one in reproducing nonlocal spreading and maintaining correct shape of the wave packet upon time evolution. Moreover, for the models considered, the fixed basis set outperforms the moving one in terms of computational efficiency. KW - Nonadiabatic quantum dynamics Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-199225 UR - https://doi.org/10.1016/j.chemphys.2019.110526 N1 - Submitted version ER - TY - INPR A1 - Titov, Evgenii A1 - Humeniuk, Alexander A1 - Mitric, Roland T1 - Comparison of moving and fixed basis sets for nonadiabatic quantum dynamics at conical intersections T2 - Chemical Physics N2 - We assess the performance of two different types of basis sets for nonadiabatic quantum dynamics at conical intersections. The basis sets of both types are generated using Ehrenfest trajectories of nuclear coherent states. These trajectories can either serve as a moving (time-dependent) basis or be employed to sample a fixed (time-independent) basis. We demonstrate on the example of two-state two-dimensional and three-state five-dimensional models that both basis set types can yield highly accurate results for population transfer at intersections, as compared with reference quantum dynamics. The details of wave packet evolutions are discussed for the case of the two-dimensional model. The fixed basis is found to be superior to the moving one in reproducing true nonlocal spreading and maintaining correct shape of the wave packet upon time evolution. Moreover, for the models considered, the fixed basis set outperforms the moving one in terms of computational efficiency. KW - Nonadiabatic quantum dynamics Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-198699 UR - https://doi.org/10.1016/j.chemphys.2019.110526 N1 - Accepted manuscript ER -