Theory of molecular opto-electronics. I - Macroscopic and microscopic response. II - Environmental effects on molecular response

Previous treatments of linear response in molecular crystals have been generalized to nonlinear response, both in a phenomenological approach and in a more fundamental approach based on microscopic response functions. A local field is defined for a suitably factorizable nonlocal polarizability response, justifying phenomenological approaches, and local field corrections in the optimization of molecular crystal optoelectronic properties for device applications, is considered. In the second part, the microscopic response coefficients of polar molecular crystals are treated. To predict the nonlinear optical susceptibilities, the molecular polarizability and hyperpolarizabilities are evaluated from molecular calculations on isolated molecules in finite fields in conjunction with crystal local-field calculations. Short-range interactions are found to modify the local molecular response and introduce new nonlocal contributions which slightly modify the dielectric theory.