The most physically and mathematically rigorous approach is to use the state-specific or singlestate MCSCF (SS-MCSCF) energy and density, allowing the free energy of the solute-solvent system to be defined similarly to the single-state case (Eq. ( )). However, it is well known that SS-MCSCF calculations for excited states suffer from the root-flipping problem, 43 making them impractical for many applications. For locating minimum energy CoIn (MECoIn), it is usually necessary that the two (or more) crossing states are orthogonal, which SS-MCSCF calculations cannot easily satisfy. Furthermore, using a single reference state may be insufficient for MRPT calculations, where multistate or quasi-degenerate MRPT methods are often required to achieve satisfactory accuracy. Therefore, a widely accepted approach for accurate quantum chemical calculations in vacuum is to average over several states during the MCSCF calculation, followed by MRPT calculations if possible. Although pursuing the SS-MCSCF approach is an interesting avenue of research, the prevailing method for excited-state calculations with multiconfigurational approaches is to SA-MCSCF.