Dear all,
I have been wondering how important is to do a wave function stability checks for transition states. I understand that they are necessary to check whether the structure is a true ground state or there is some lower state. As far as I see, most of TSs correspond to the formation/cleavage of bond/bonds so we might expect. for example, formation of range-separated bi-radicals which are not described well by single-reference approaches such as DFT, so they will be unstable per se. What should be done to get credible TS structure and energetics in that case? Should one use only multi-reference approach for such reaction pathways or DFT might be still suitable?
I would appreciate any suggestions, comments or references.
Thank you for your time,
Nikita.
Dear Nikita,
You may access the following links:
https://chemistry.stackexchange.com/questions/76636/when-is-it-necessary-to-check-wavefunction-stability-in-density-functional-theor
https://chemistry.stackexchange.com/questions/103387/what-exactly-is-meant-by-multi-configurational-and-multireference
Hoping this will be helpful,
Rafik
Rafik Karaman, thank you for the links. They are helpful, however, the issue of application of wave function stability test to transition states is not discussed. So, I am still wondering whether it is meaningful or not.
In short, I believe it can be meaningful (depending on the case) and DFT can be used for evaluating the wave function stability. In fact, a Broken Symmetry approach could be possibly adopted to verify the stability of the TS solution at DFT level.
I am successfully using this approach for the GS configuration of metal complexes showing a singlet/triplet instability. Moreover, I used BS calculations for spin-crossover iron(III) complexes (Article Structural Diversity on a New Series of Halogenated Quinolyl...
)An step-by-step example of application of the BS approach to GS configurations can be found here: https://gaussian.com/afc/.
I hope this may be of help.
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