I wanted to study the effect of solvent concentration in some properties of molecule?
Mr. Safy,
You can do this using the PCM methods at different dielectric constant values. For dilute solutions of ionic species, if your system is ionic one, you can use the equation (1) (attachment) for example giving the analytical relationship between the dielectric constant and the concentration of the salt via Langevin's function. With increasing in the concentration you should take into consideration the solute-solute interactions. How? You should used MD/MM optimization of ensembles of interacting ionic pairs with different number. Then you should use again PCMs employing the corresponding dielectric constant at the given concentration. For some systems, using equation (1) you even do not need to perform measurements. All the parameters can be obtain by Gaussian.
When you have non-ionic molecules, with low dipole moments, you can use equation (2), for example (Ingham-Ely's equations), again giving the information about the dielectric constant, however through the viscosity. If you have data about the density of your systems at different concentrations you can use also the Clausius-Mossotti' equation (equation 3) (attachment). The computations of ensembles are valid for those systems as well after a critical concentration values.
If you have not some of those data they can be measured. Those are basic physico-chemical measurements. On this base you can obtain for example linear optical and NLO properties in solution and their function of the concentration, for example. Or magnetic properties as function of the concentration, pressure, ionic strength and so forth.
The topic of your questions is related to chemical hydrodynamics, thermodynamics, transport phenomena, and the like, rather than to capability of Gaussian.
There are developed theories even for more specific and complex systems at given explicit conditions, which allow you to compute further by Gaussian other properties of interest as mentioned above, using PCMs approaches. In other words, depending of your system of interest, some of the parameters can be neglected or approximated in order to reduce the number of computations by Gaussian.
Dear Mohamed,
There is no such approach in Gaussian 09. You should look for another software if available.
Rafik
Mr. Safy,
You can do this using the PCM methods at different dielectric constant values. For dilute solutions of ionic species, if your system is ionic one, you can use the equation (1) (attachment) for example giving the analytical relationship between the dielectric constant and the concentration of the salt via Langevin's function. With increasing in the concentration you should take into consideration the solute-solute interactions. How? You should used MD/MM optimization of ensembles of interacting ionic pairs with different number. Then you should use again PCMs employing the corresponding dielectric constant at the given concentration. For some systems, using equation (1) you even do not need to perform measurements. All the parameters can be obtain by Gaussian.
When you have non-ionic molecules, with low dipole moments, you can use equation (2), for example (Ingham-Ely's equations), again giving the information about the dielectric constant, however through the viscosity. If you have data about the density of your systems at different concentrations you can use also the Clausius-Mossotti' equation (equation 3) (attachment). The computations of ensembles are valid for those systems as well after a critical concentration values.
If you have not some of those data they can be measured. Those are basic physico-chemical measurements. On this base you can obtain for example linear optical and NLO properties in solution and their function of the concentration, for example. Or magnetic properties as function of the concentration, pressure, ionic strength and so forth.
The topic of your questions is related to chemical hydrodynamics, thermodynamics, transport phenomena, and the like, rather than to capability of Gaussian.
There are developed theories even for more specific and complex systems at given explicit conditions, which allow you to compute further by Gaussian other properties of interest as mentioned above, using PCMs approaches. In other words, depending of your system of interest, some of the parameters can be neglected or approximated in order to reduce the number of computations by Gaussian.
These are very useful answers thank you Prof.karaman, Mr hosseini and very big thanks prof. Ivanova
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