For example, I performed calculations to evaluate binding energy for a complex (let us assume A-B) using TURBOMOLE and by taking same structures i tried to find out the bonding energy contributions using ADF. Both the values (binding energy and total bonding energy) differs quite a bit (by 40-100 kcal mol-1). I know that the level of calculations can contribute significantly to these parameters. Thus, I have used almost same computational level for both the software. For ADF, as it uses slater type basis set, TZ2P is used while for TURBOMOLE, TZVP is used. It would be a great help if anybody expalin the defination of the term and their differences.
Dear Prof Gert,
Thanks for the answer. I think the problem was with my understaning. I want illustrate my question a bit. In my case, I wanted to know binding free energy (gibbs free energy) for a metal inside a protein cavity. So, I used following equations for free energy:
Metal + Protein = Metal-Protein
The entropic contribution is indeed an important factor. I found delta G : -20 kcal/mol (where delta H= -30 kcal/mol).
But in case of ADF i took protein and metal as a fragment and tried to calculate bonding energy (morokuma type) for Metal-Protein (which is sum of electrostatic, orbital contributions and dispersion factor). The resulted bonding energy are -170 kcal/mol.
As in the fragments, it took the coordinates (geometries) from the complex structures thus the calculated bonding energy certainly do not corrleate to the free energy term.
Thanks again for the attachment.
Biswajit
Dear Biswajit,
Indeed you wouldn't expect a 100 kcal/mol difference in binding energies if you use the same functional and a reasonably large basis.
Without looking at your input/output files it's hard to say what may be going on.
Perhaps you can share your ADF files on the ADF mailing list?
http://lists.scm.com/pipermail/adflist/
ADF users and developers are subscribed there, whereas I don't know if many people would find your question on ResearchGate.
Best wishes,
Fedor
- Badges
- Science topic
- Similar topics
- Chemistry
- Theoretical Chemistry