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Exploring Bethe-Salpeter Excited-State Dipoles: The Challenging Case of Increasingly Long Push-Pull Oligomers.

Iryna KnyshJose D J Villalobos-CastroIvan DucheminXavier BlaseDenis Jacquemin
Published in: The journal of physical chemistry letters (2023)
The change of molecular dipole moment induced by photon absorption is key to interpret the measured optical spectra. Except for compact molecules, time-dependent density functional theory (TD-DFT) remains the only theory allowing to quickly predict excited-state dipoles (μ ES ), albeit with a strong dependency on the selected exchange-correlation functional. This Letter presents the first assessment of the performances of the many-body Green's function Bethe-Salpeter equation (BSE) formalism for the evaluation of the μ ES . We explore increasingly long push-pull oligomers as they present an excited-state nature evolving with system size. This work shows that BSE's μ ES do present the same evolution with oligomeric length as their CC2 and CCSD counterparts, with a dependency on the starting exchange-correlation functional that is strongly decreased as compared to TD-DFT. This Letter demonstrates that BSE is a valuable alternative to TD-DFT for properties related to the excited-state density and not only for transition energies and oscillator strengths.
Keyphrases
  • density functional theory
  • molecular dynamics
  • high resolution
  • high speed