Quantum chemical calculations of the first- and second-order hyperpolarizabilities of molecules in solutions

A study of the effect of solute/solvent interactions on static and dynamic molecular hyperpolarizabilities (beta and gamma) of series of prototypical pi -conjugated donor-acceptor chromophores is presented. The solvent effect was included via a recently proposed discrete quantum-mechanical Langevin dipoles/Monte Carlo method. The nonlinear optical properties (NLO) were computed using the INDO-like Hamiltonian based finite-field (FF) and sum-over-states (SOS) methods implemented in the GRINDOL code. The calculated beta(gamma) values are compared with experimental data determined in solution phase EFISH(THG) measurements and other published theoretical works. Generally, a reasonable agreement between calculated and experimental data was obtained. Moreover, our results indicate that the QM/LD/MC model gives a correct description of the solvent effect on the nonlinear optical response of molecules. It suggests that this level of theory can be used as an effective tool for investigation of NLO properties in condensed phases.