We have tried to study a hydrolysis mechanism using Gaussian 09 programme for a trans platinum complex both in gas as well as in solvent medium. In this study, we have used only one explicit water molecule. Since, in my case, it is a two step hydrolysis process and at each step only one water molecule at a time is taking part. If we considered more water molecules into the system than what will be the effect on the overall results. Is it necessary to consider more than one water molecule into the system to study the hydrolysis porcess?
Dear Iftikar Hussain,
Generally in my DFT calculations, I use one molecule of water; this molecule acts as a a nucleophile. However, in some cases where the hydrolysis is catalyzed by an acid or base I use two water molecules: the second water molecule can donate H+ or OH- depending if the hydrolysis is acid or base-catalyzed reaction.
IF you reaction is not catalyzed by an acid or base you can use one water molecule, then take the optimized structure and run calculation with solvent dielectric effect, PCM model where the dielectric constant of water is 78.39.
Hoping this will be helpful,
Rafik
Thanks you very much Rafik Karaman sir for your valuable suggestion.
In my case I have use only one water molecule, which will later going to replace the Cl ion, this is not an acid or base-catalyzed reaction.
As you suggested, I have also made the study of solvent effect using CPCM model (dielectric constant=78.39).
My point of concern is about the dispersion forces. If we consider more water molecule into the system than only the role of dispersion contribution have to be consider. Is not it?
Dear Iftikar,
Yes. In this case you might add some of Truhlar keywords:
For appropriate keywords, please use the following link:
http://www.gaussian.com/g_tech/g_ur/k_dft.htm
Rafik
thanks sir. This will be very much helpful for my research work.
Regards,
Iftikar
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