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Time-dependent Density Functional Theory has been around for quite a while now, seeing Density-Functional Theory for Time-Dependent Systems, and so it has been developed extensively, implemented in major codes, and succeeded by more modern and accurate methods that may be used in research.

However, TD-DFT is still more efficient than some of those methods, and it is most likely very well regarded still in the fields of photophysics and photochemistry.

I am trying to make sense of its capabilities and limitations, particularly in the fields of photophysics and photochemistry.

What are some key references where TD-DFT successfully predicted or reproduced an important result in photochemistry?

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    $\begingroup$ +1 But what is meant by "some of those methods" ? I very much like this question, but it might be able to use some proof-reading! @Anyon and I fixed some of the errors already. $\endgroup$ Mar 4, 2021 at 19:36
  • $\begingroup$ I agree! I will edit the question to make it more clear and specify what is meant. $\endgroup$ Mar 4, 2021 at 20:00
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    $\begingroup$ I think TD-DFT is exact in principle but, just as in ground-state DFT, the accuracy depends on the XC functional, your basis set, and calculation parameters. Additionally, TD-DFT needs to be combined with molecular dynamics or Monte Carlo methods if you're interested in accurately reproducing dynamical properties (e.g. band widths of UV-Vis spectra). $\endgroup$
    – Hayden S
    Mar 13, 2021 at 22:54
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    $\begingroup$ I would feel comfortable answering this question as what TD-DFT can do and where it fails, rather than giving specific examples. What is considered photochemistry and "successful" is pretty broad. $\endgroup$
    – Cody Aldaz
    Oct 20, 2021 at 19:37
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    $\begingroup$ @CodyAldaz I think that would make for a good answer $\endgroup$
    – Tyberius
    Oct 30, 2021 at 0:18

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Well, certainly TD-DFT is not perfect, there are more accurate methods, but it's so popular since it's so efficient and much faster when compared to these other methods. Anyway, regarding your question, this a new paper published recently, and it shows very good correspondence with experimental data using TD-DFT: https://journals.aps.org/prx/abstract/10.1103/PhysRevX.12.011012

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A recent non-obvious one has been the use of TD-DFT to look at vibrational couplings in singlet fission in pentacene. The sequence of electronic transitions works like this:

  • Optical absorption creates a spin-singlet excited state. This is fast.
  • But that has a spin-allowed and energy- and entropy-favorable transition to a bound triplet pair. So this lives for 30-80 fs only.
  • Triplet pair dissociates, and triplets are long-lived (nano- to microseconds).

The excited state was found to couple to a few vibrations, most notably a 1-THz one. The TD-DFT results agreed with experimental ultrafast electron diffraction.

Source: https://www.science.org/doi/full/10.1126/sciadv.abg0869

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