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Perturbation and Time-Dependent DFT


This was very complex, so here are some takeaways:

  • TD-DFT is generally better for excitations than CI due to the direct inclusion of correlations, but is naturally very functional/situation dependent.
  • Charge transfer transitions are not well modelled using TD-DFT. This is due to self-interaction issues, causing lower energy excitations.
  • TD-DFT works best with a bit of HF exchange (typically ~25%) - e.g. B3LYP, PBE0
  • Certain functionals are better for Rydberg states, when they account for longer range behaviour.ß