Hello everyone,
I do calculations on compounds with about 25-30 atoms (hydrogen, carbon, oxygen) and about 110 electrons in a water solvent (SMD solvation model). These are optimizations and frequency calculations. I'm searching for the best reference method I could compare results with. These systems are being calculated with B3LYP/6-311**G(d,p), B3LYP/aug-cc-pVDZ and B3LYP/aug-cc-pVTZ.
I was thinking about CIS/6-311++G(d,p) but have found it's not the best pick - it's barely accurate when calculating frequencies. So I came up with an idea to recruit CCSD/cc-pVTZ, though three things are running through my head:
The main problem arises from the technical features of the computer I'm using and time. What's is your opinion? Maybe use something completely different?
Thank you.