Hi Jonas,

it is indeed possible to run CC2 on HF/COSMO orbitals. The shift will be small, however,

and I am not sure, if this shift will always go in the right direction.

You will neglect the COSMO contributions to the correlated ground state energy as well as

the contributions to the excitation energy. Since there is not much known about these

contributions, it is not clear, how much you are neglecting.

A first step to include some solvation effect, that is maybe a bit more safe, could be to

optimize ground state geometry on DFT/COSMO or MP2/COSMO level, instead of using

gas phase geometries.

Cheers,

Arnim