What's the appropriate analysis to study the interactions in a transition state?

aitouna

Dear Professor Tian Lu,What's the appropriate analysis or method to study the interactions in a transition state ?
* Symmetry-Adapted Perturbation Theory (SAPT) using Psi4 program, or,
* Using Multiwfn program for NCI analysis.


Sincerely,

aitouna

Dear Professor Tian Lu,
Thank you very much for the clarifications, and thank you very much for clearing up the confusion.


Sincerely,

sobereva

aitouna 发表于 2020-3-26 01:18
We can consider each reactant as a fragment, the m-cpba is the fragment 1 and the other reactant is  ...

To use SAPT, the two fragments should not be connected by chemical bond, because which is "strong" interaction and cannot be properly described by intermolecular perturbation theory. At your TS structure, your division of the two fragments involves breaking chemical bond, therefore SAPT cannot be used.

aitouna

We can consider each reactant as a fragment, the m-cpba is the fragment 1 and the other reactant is the fragment 2.

sobereva

aitouna 发表于 2020-3-22 21:47
Dear Professor Tian Lu,
Thank you very very much for your prompt reply and the wonderful clarificat ...

It is better to upload the image of your TS structure and explicitly show how do you want to divide the system as two fragments.

aitouna

Dear Professor Tian Lu,
Thank you very very much for your prompt reply and the wonderful clarification.
But, only for the study of non-covelent interactions, in a transition state there is fragments (two fragments), so why the SAPT doesn't work ?

sobereva

SAPT is only suitable for weak interaction, evidently it doesn't work for interfragment interaction at TS status.

The NCI method in Multiwfn can be used to analyze weak interaction in TS geometry, however if you are interested in variation of chemical bonds, you should use such as AIM, ELF/LOL, bond order... to perform the analysis, all of them can be easily realized via Multiwfn. See Section 4.A.11 of Multiwfn manual for an overview of methods for studying chemical bonds.

In addition, the Distortion/Interaction analysis may be useful, see review articles: Angew. Chem. Int. Ed., 56, 10070 (2017), WIREs Comput. Mol. Sci., 5, 324 (2015)