I am optimizing a molecule, benzenesulfonamide derivative, using the following route:
"# opt b3lyp/6-31g geom=connectivity"
Everything worked smoothly, however, I have an issue with the converged structure. Apparently the most energetically favored geometry is the one with the amine group disconnected from the sulfonyl group...what???. See attached
My Gaussian version is Gaussian 09W and the molecule specification is also attached in this message.
Any idea?
P.S: I used either an octahedral or tetrahedral sulfur for the same work...none of them gave me a reasonable geometry
Eduardo Cueto Diaz
your command # opt b3lyp/6-31g geom=connectivity" so you can add pop=full
May be it will be solve.
Waseem Ahmad Ansari , I obtained the same inconsistency localized in the same group. The amine disconnects from the sulfone...
This is really frustrating.
Actually, it happened with the triflate group as well, the -CF3 part disconnects from the SO2.
Any other ideas?
Waseem Ahmad Ansari , here you have it (the input file).
Thank you for your help
Yes, this is something that I will try as well.
In your optimized job the double bonds/resonance is lost in the sulfonamide group, I think that computing sulfonyl groups is a tricky business
Thank you for your help
I could not understand the image you posted. Look at the bond distance between N and S. If that is legitimate, don't worry. Visualizers make these problems. By the way, you can change the functional, B3LYP is not black box
Prasanta Bandyopadhyay Me neither!, XD. That's why I asked where is the error.
I changed the basis set and now it's working, it converged properly. Thank you again Waseem Ahmad Ansari
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