The electron density polarization analysis based on electron excitations proposed in J. Phys. Chem. A, 124, 633 (2020) has been implemented as subfunction 17 of main function 18. This method is able to provide very valuable insight into the nature of electron density polarization under an external perturbation (e.g. point charge), and can be used to study substitution effect, mechanism of electrophilic/nucleophilic reactions, atomic polarizability, and so on. See Section 3.21.17 of Multiwfn manual for introduction and Section 4.18.17 for example.