I agree with you that increasing the weight of the state of interest
might be a solution, with the limiting case of a state-specific
MCSCF. This, I think, would be the best option, if possible.
However, in my experience it can be quite hard to achieve
convergence on a SS-MCSCF geometry optimization for an excited state,
unless one has symmetry labels to help the choice of the reference.
In those cases where SS-MCSCF won't converge, and I bet there
are many, SA-MCSCF + state-specific solvation gradients can be
a good compromise.
On Tue May 28 '13 6:36pm, Alex Granovsky wrote
>>thanks for the reply. Actually it might be a good idea to
>>implement a state-specific solvation for MCSCF.
>>An interesting case is when a system has an excited state with
>>a charge-transfer character. In that case using an average density
>>might give an unexpected result, but I might be wrong.
>I do not agree with this. Consider SA-CASSCF over two states,
>the ground state with no charge-transfer and the first excited
>state of charge-transfer type. If one is using field generated
>by the averaged density then both states are not described
>very good. However, they are least approximately described
>on an equal footing. If one is using reaction field from the
>second state, at the first glance S1 state becomes much better
>described. At the same time the ground state becomes described
>very poorly. Even worse, because S0 is now not well described,
>in SA-MCSCF procedure S1 state will tend to partly mimic S0 state
>and thus, actually even S1 state will become not such a well described.
>Perhaps if one is interested in describing S1 state only,
>then this approach may work. However, I'd prefer just to
>increase to the weight of S1 state in state-averaging.
>>Concerning the gradients, is there a theoretical reason why
>>they should be disabled? or is it just a technical problem?
>Because at least at the first glance this modified MCSCF procedure
>will not be longer compatible with our implementation of gradients
>for SA-MCSCF (http://classic.chem.msu.su/gran/gamess/ss-gradients.pdfhttp://classic.chem.msu.su/gran/gamess/ss-gradients.pdf).
>However, this may requre a more detailed analysis.