The QM/MM models capture the chromophore-solvent electrostatic interaction and solvent→chromophore polarization explicitly through electrostatic embedding. If a non-polarizable force field description (such as TIPnP) is adopted for the solvent molecules, then each solvent molecule acquire several or more fixed-value point charges. Together, the solvent point charges provide an electrostatic embedding potential that interacts with and polarizes the chromophore electron density.