DFT is not variational.
Best regards,
Ye Mei
ymei.itcc.nju.edu.cn
Institute of Theoretical and Computational Chemistry
Key Laboratory of Mesoscopic Chemistry
School of Chemistry and Chemical Engineering
Nanjing University
Nanjing 210093
P.R.China
2007-01-19
======= 2007-01-19 23:40:10 FyD wrote=======
>Dear All,
>
>I try to develop a bunch of new FF parameters by fitting MM energies
>to QM energies. As first tests, I decided to fit the FF dihedral
>parameters to data generated to the B3LYP/6-31+G**/HF/6-31G* &
>MP2/6-31+G**//HF/6-31G* theory levels. Since my model is a little big,
>I think I cannot afford MP4 energies.
>
>In FF development and to get QM single point energy, what theory level
>is the best, I mean for taking into account electron correlation: MP2
>or B3LYP ?
>
>I would answer MP2, however I was quite surprised to see that the
>B3LYP energies are smaller than the MP2 ones.
>
>Thank you, regards, Francois
>
>
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Received on Sun Jan 21 2007 - 06:07:38 PST
