A group–dipole interaction model of the molecular polarizability and the molecular first and second hyperpolarizabilities

The group–dipole interaction model is generalized to treat the molecular polarizability and the molecular first and second hyperpolarizabilities. A molecule is divided in groups; each group is characterized by a polarizability and by first and second hyperpolarizabilities, and it resides in an internal molecular electric field. The internal field is thought to arise from any charges or permanent moments within the molecule, and it is characteristic of the system being studied. In the point dipole approximation, all the dipole–dipole interactions are treated exactly, and all the molecular results are written in terms of only those quantities needed to calculate the molecular polarizability. Several approximate theories are considered, and the additivity of group polarizabilities and hyperpolarizabilities is discussed. Special formulas are derived to treat an assembly of interacting isotropic atoms.