The mutual polarization of reactants: Fukui function description of the charge reorganization

The diagonal and off-diagonal Fukui functions (FFs) constitute the charge transfer FF that describes reorganization in the electron density due to charge transfer. In this Letter, we consider the mutual polarization of the reactants. We prove that the off-diagonal FF is related to charge reorganization due to the polarization process. The change in the electron density of a given reactant caused by a perturbation in the external potential (due to nuclei) is proportional to the off-diagonal FF. The self-consistent charge and configuration method for a subsystem is used to illustrate this concept numerically.