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patonlab / GoodVibes

Calculate quasi-harmonic free energies from Gaussian output files with temperature and other corrections
http://www.patonlab.colostate.edu
MIT License
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Bav = 10.0e-44 #24

Closed pascalfriederich closed 5 years ago

pascalfriederich commented 5 years ago

Dear GoodVibes developers,

I tried to reproduce the entropy contributions in the low frequency limit (Grimme, DOI: 10.1002/chem.201200497) and I discovered that you are using a value of BAV of 10.0e-44 (line 1922 in GoodVibes.py) while Grimme suggested in his paper to use 1e-44. Was it your intention to change this value or just a typo in the code?

Best regards, Pascal Friederich

bobbypaton commented 5 years ago

Good spot, thanks! I played around with this value to see its effect and it's possible that it got changed at some point from the value in Grimme's original CEJ paper. In testing, changing by an order of magnitude didn't seem to give rise to noticeable effects - in this case, I have now changed it back to 1e-44, which for our systems leads to a difference of around 2 microH (0.001 kcal/mol) in free energy at 298K.

bobbypaton commented 5 years ago

When we played around with B(av) between 1e-45 to 1e-43 (DOI: 10.1021/acs.joc.8b02436) the variation on the absolute free energies was on the order of 0.1 kcal/mol, although for free energy differences the effect was about 0.01 kcal/mol.

pascalfriederich commented 5 years ago

Thank you!