As stated for Eq. ( ), in the current QM/DIM scheme, the contribution of the MM region only comes from the induced charges and dipoles by the second-order potentials and fields of the QM counterpart, where the induced dipole moments are proportional to the first power of the field intensity. MNP may possess a strong nonlinear response, and the induced dipole moments should include the nonlinear terms that are proportional to the second and higher powers of the field intensity. Therefore, it is reasonable to account for the nonlinear response of MNPs.