The UV absorption energy spectrum of a molecule has been recorded experimentally using binary solvent (CH3Cl:CH3OH =10:1 v/v). I am trying to calculate the absorption energy of the same molecule using computational methods. For that I want to give the same solvent mixture (CH3Cl-CH3OH =10:1 v/v) in my DFT calculation.
How can I prepare the input file for Gaussian? What are the keywords that are used in Gaussian for binary solvents?
Dear Tabti Hanane,
I think it is not possible to carry out this kind of calculation with gaussian as it extends PCM scope... Maybe you could use a linear combination of your solvents values to make your calculation, but I prefer waiting for more background in this sort of problem by my colleagues.
Just a wild guess, If you can measure the Dielectric constant of the mixture, then you can put the value at the SCRF section. Have a look if that works.
I agree with the two answer above (Corentin Lefebvre and Prasanta Bandyopadhyay) which are supposed to approximate the real environment of a molecule. In fact, the true relative permittivity ("dielectric constant" is obsolete) is not exactly a linear combination of the individual permittivities, but non-linearities are highly dependent on the solvent properties. In the real solvation shell around a molecule, differential solvation should be considered: for example in a water/acetonitrile mixture, H2O, being a H-bond donor, may interact with a H-bond acceptor solute, and more H2O than ACN may be present around the solute.
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