I am about to compute reaction steps for a series of compounds using DFT. A key point in our discussion is the dependency of the experimental rate of reaction w.r.t. solvent used, so it is very important that we incorporate solvation effects in our computational models.
I am aware of the best practices in choosing functionals, dispersion corrections, basis sets, etc.. By reading a little I decided on using the SMD model for implicit solvation. I may use either ORCA or NWChem.
My questions are:
- a. Should geometries be optimised in solvent, in the gas phase or both? b. In case I use only gas phase geometries, should I calculate frequencies using implicit solvation (I doubt) or can I use the calculated free energy of solvation (done in a single point calculation) to correct the gas phase free energy?
- a. In case I decide on using (one or two) explicit solvent molecules to better model the system, are there best practices on using them together with an implicit solvation model (in terms of calculating free energy of solvation and in deciding when it has converged/is adequate)? b. What about the points addressed in 1. (gas phase versus condensed optimisation and frequency calculations) for this case?
References from literature are greatly appreciated. I am looking forward to hear from you!