Firefly and PC GAMESS-related discussion club

 
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David G.
david.grifith@gmail.com

Dear Alex

>sorry for overlooking that.

many thanks for your help and reading the forum in details. It's your great favor.


>Actually my question was on the origin of -18.394 KJ/MOL correction.
>I see it is taken from the vibration analysis, is it?.


yes, it has such terms since if I understand well it was proposed by FF to calculate free energy in gas then compare it with the free energy of the system in solvent.

NOTE THAT THE FREE ENERGY IN GAS PHASE IS NOT EQUAL TO
THE -INTERNAL ENERGY IN SOLVENT- WHICH WAS USED TO COMPUTE
VARIOUS QUANTITIES AND CONTRIBUTIONS ABOVE. THIS MEANS
THAT YOU NEED TO PERFORM SEPARATE GAS-PHASE CALCULATIONS
TO COMPUTE FREE ENERGY IN GAS PHASE AND GET ENERGY CHANGE
WHEN GOING FROM THE GAS PHASE TO SOLUTION


>I think PCM energies you have computed do not include these types
>of contributions. It would be more correct to compare -100.426656 H directly with -100.433893 H and -100.430009 H.



yes it seems that the free energy in solvent doesn't contain translational, rotational, and vibrational terms of Gibbs free energy. So the question that is arising from that is why we do call it free energy and why FF does propose to calculate free energy in gaseous state. Is that free energy something else ?



Sincerely Yours,
David