@unpublished{HumeniukBužančićHocheetal.2020,
  author    = {Humeniuk, Alexander and Bužančić, Margarita and Hoche, Joscha and Cerezo, Javier and Mitric, Roland and Santoro, Fabrizio and Bonačić-Koutecky, Vlasta},
  title     = {Predicting fluorescence quantum yields for molecules in solution: A critical assessment of the harmonic approximation and the choice of the lineshape function},
  series = {The Journal of Chemical Physics},
  journal   = {The Journal of Chemical Physics},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-199305},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@unpublished{TitovHumeniukMitric2020,
  author    = {Titov, Evgenii and Humeniuk, Alexander and Mitric, Roland},
  title     = {Comparison of moving and fixed basis sets for nonadiabatic quantum dynamics at conical intersections},
  series = {Chemical Physics},
  journal   = {Chemical Physics},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-199225},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@unpublished{TitovHumeniukMitric2020,
  author    = {Titov, Evgenii and Humeniuk, Alexander and Mitric, Roland},
  title     = {Comparison of moving and fixed basis sets for nonadiabatic quantum dynamics at conical intersections},
  series = {Chemical Physics},
  journal   = {Chemical Physics},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-198699},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}