Calculations of Nonlinear Optical Properties for the Solid State

This chapter deals with the oriented gas model that employs simple local field factors to relate the microscopic to the macroscopic nonlinear optical responses. The supermolecule and cluster methods are presented as a means of incorporating the various types of specific interactions between the entities forming the crystals. The field-induced and permanent mutual (hyper)polarization of the different entities then account for the differences between the macroscopic and local fields as well as for part of the effects of their surroundings. Other methods for their inclusion into the nonlinear susceptibility calculations are reviewed. The specifics of successive generations of crystal orbital approaches for determining the nonlinear responses of periodic infinite systems are presented. Finally, we consider both semiempirical methods, which typically incorporate the experimental susceptibility into the evaluation of the nonlinear responses, and techniques for determining the in-crystal ion hyperpolarizabilities as intermediates for evaluation of the susceptibilities of ionic crystals.