I actually have a general question about the differences between SCRF=PCM and SCRF=SMD in G09. As far as I know, in theory SMD includes corrections for CDS (cavitation, dispersion and solvent structure effects) while PCM does not. In practice, SMD distorts and reorients the gas optimized structures much more than PCM does and also SMD gives more accurate solvation energies compared to PCM ( though SMD has been parameterized more carefully on a large number of input solvation free energies, so its success over PCM may be just as a result of its optimized parameters for delta G and not because of its more realistic structure !?). So, is the more distorted SMD optimized geometry more reliable than PCM? In fact, I have not seen many papers using SMD??
The other question is that are vibrational IR frequencies calculated with SCRF optimized geometry reliable or preferable over vacuum frequencies? And if yes, since the normal mode vibrational frequencies calculated at SMD differs with those obtained by PCM, which one is more reliable?
I agree with Shrinwantu, but you have to also bear in mind that the SMD model was developed/parametrized to work with the Minnesota functionals family (i.e. Truhlar's M05, M06 etc.), so its not just about the solvation model itself but rather of the whole level of theory including the solvation model.
Check out the abstract from the original Truhlar's model:
https://cheminfographic.wordpress.com/2017/06/30/fundamental-organic-mechanisms/
From your words, it looks like SMD may be a better choice. Have you tried COSMO?
Yes, I have tried COSMO in ADF code and it gives similar results to SMD.
I am more towards SMD too.
Everyone has their own viewpoint, and I fear there is no direct answer. The linked paper is just one of many.
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532016001102055
I agree with Shrinwantu, but you have to also bear in mind that the SMD model was developed/parametrized to work with the Minnesota functionals family (i.e. Truhlar's M05, M06 etc.), so its not just about the solvation model itself but rather of the whole level of theory including the solvation model.
Check out the abstract from the original Truhlar's model:
https://cheminfographic.wordpress.com/2017/06/30/fundamental-organic-mechanisms/
Usually, SMD method provides results with more accuracy than PCM method, principally for calculation of free energy of solvation involving ions in polar solvents. If the geometry had a distortion with SMD and with PCM had not, I should trust at SMD geometry. A good test is to use other method like COSMO, but as you mentioned COSMO provided the same result of SMD.
When you calculate the Free energy with the vibrational frequencies using SMD have a incorporation of some solvation entropy. Thus, the free energy results are not so overestimated like when you use the thermodynamic corrections at gas-phase in the SCRF electronic energies.
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