Finite-field calculations of the second-order hyperpolarizabilities γ of molecules in solutions

The results of the semi-empirical computation of the second-order hyperpolarizabilities γ for molecules in the gas phase and in solutions are presented. The finite-field formalism was used to calculate individual components of γ tensors. The solvent effect was included via the quantum-mechanical Langevin dipoles/Monte Carlo approach. The calculations demonstrate the existence of the large solvent effect on the second-order hyperpolarizabilities of the charge-transfer type of non-linear optical chromophores. The calculated γ values, including the solvent effect, are compared with experimental data determined in solution phase THG measurements.