On the calculation of local field factors for microscopic static hyperpolarizabilities of molecules in solution with the aid of quantum mechanical methods

We present a simple computational method to connect the computed ab initio values of static dipole polarizabilities and hyperpolarizabilities of molecules in solution with their experimental counterparts. The connection is done in terms of local field factors. We show that formulas used by experimentalists are not adequate, and that they can be replaced by a reformulation of the quantum-mechanical codes for the calculation of (hyper)polarizabilities in solution by using a realistic description of the solvent reaction field (i.e., a cavity withthepropermolecularshape). Thisreformulationleadstoanadditionalsetofhyperpolarizabilityvalues whichtakeintoaccountlocalmodificationstotheexternalstaticfield. Thissecondsetofvalueshasadirect relation with the macroscopic susceptibility tensors and, when compared to that derived from standard calculations, allows one to evaluate realistic local field factors.