I am working on the polycarbonate compound. I would like to know which basis set will give me good data closer experimental values of frequency, geometrical parameters, reactivity details and other related values.
Hello Xavier,
You can try with TZV basis. It is enough big to give good result and not too much bigger to cost too much time. With dft you could have a good geometry and good vibrational part. A base that gives me a very good results are B3PW91.
On the other hand, if you want good numerical results (thermochemistry...) you could consider apply compound methods like CBS-QB3 or APNO or increasing more the accurate calculation, you can use "MP2" or CCSD(T)/cbs*, where cbs is an extrapolation with minimum three different basis like DZV, TZV and QZV or other kind of "complete basis set".
I hope it helps you,
Joaquim Rius
UAB
Hello Xavier,
I attach one of my results with different methods.
You should try with a TZV Pople's basis set, some times they are more accurate and lighter than Dunning's. I sugest not to use MP2 if you want termodinamics, rather use CCSD(T)
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