Quoting Michel Becker <michelbeacker.web.de>:
> During my search in the archive, I found that it's strongly
> recommanded to use as well for the geometry optimisation 6-31G* (NOT
> the ESP calculation), but actually I am quite sure, that I've read
> once here that some people used higher ones for the optimisation.
>
> Am I wrong? I would be nice, if someone would be so kind and would
> give me a short answer.
It depends which FF you are interested in...
For the Cornell et al. FF (parm94, parm96, parm98, parm99):
- For geometry optimization, the authors used the HF/6-31G* theory level.
- For MEP computation, the HF/6-31G* theory level was also used.
However, here this is to
generate implicite polarization.
See for instance in R.E.DD.B. the projects W-46 or F-60
All the computational conditions are available in a R.E.DD.B. project;
i. e. not only the charge values...
http://q4md-forcefieldtools.org/REDDB/up/W-46/
http://q4md-forcefieldtools.org/REDDB/up/F-60/
For Duan et al. FF (ff03):
- For geometry optimization, the authors used the HF/6-31G** theory level.
- For MEP computation, the B3LYP/cc-pVTZ theory level in diethylether
was used.
See for instance in R.E.DD.B. the projects F-66, F-68 & F-70
http://q4md-forcefieldtools.org/REDDB/up/F-70/
More generally, I think you can use higher basis sets in the geometry
optimization step, while you have to rigorously follow the theory
level used in the MEP computation.
regards, Francois
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Received on Sun Mar 25 2007 - 06:07:13 PDT
