From: Aleksei (
Date: Wed Apr 13 2022 - 20:53:46 CDT

Optimize that angle in a different model molecule that has no phenyl
hydrogen nearby, then copy the parameter to your molecule of interest

El 13/4/22 a las 13:33, Daniel Fellner escribió:
> It's me again,
> During some angle optimisation, I noticed two angles terminating in
> carbonyl carbon were converging to unbelievably low force constants.
> Testing these parameters in MM minimisation shows these angles deviate from
> QM even more than the original parameters.
> I believe the issue is favourable 1,6 interactions between the carbonyl
> oxygen and a phenyl hydrogen nearby, contaminating the resulting PES.
> What's the best course of action? Exclude these angles from optimisation?
> Recalculate the Hessian at a geometry lacking these interactions?
> Iteratively fit these guided by IR? Or is there some way to decouple the
> interaction during optimisation/Hessian calculation?
> Kind regards,
> *Daniel Fellner BSc(Hons)*
> PhD Candidate
> School of Chemical Sciences
> University of Auckland
> Ph +64211605326