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Alex Granovsky
gran@classic.chem.msu.su

your question is related with similar question on
the EFP model with CIS and TD in Firefly
asked by Sanya some time ago.

In brief, with Firefly, calculation of excited states within implemented
PCM (or EFP, or SCRF) + CI/TD approach corresponds to ultrafast,
strictly non-adiabatic initial excitation process so that the
polarization of solvent is still exactly the same as in the case
of ground, SCF state. This is usually good for excitation spectra
but clearly not for equilibrium properties of the excited states.

On the other hand, the self-consistent PCM (or EFP, or SCRF) + CI/TD
model (that is not implemented at present) would correspond to
the equilibrium solvation of the excited state.

Regards,
Alex Granovsky


On Fri Jan 29 '10 1:58am, Pedro Silva wrote
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>Dear friends,

>I have a system composed of two neutral molecules, A and B. Upon excitation with light, an electron moves from A to B. I want to characterize this charge-transfer excited state as A an B are moved toward each other, and due to the large size of the molecules I can only afford to do that with CIS.

>I ran a CIS computation of the A - B system at different A-B distances, and got a sensible result in the gas phase: as the A-B distance decreases, the charge-separated excited state becomes more stable (about 30 kcal.mol-1 lowering from 100 to 8 angstrom). From inspection of the Coulomb law (ether with point charges or dipoles) I expected that in solution, this stabilization should be smaller by a factor similar to the solvent dielectric constant. However, when repeating the computation with PCM turned on I got almost the same result as in the gas phase (+/- a few kcal.mol-1). Any ideas why?

>Thanks!
>Pedro