Solvent effects nonlinear response

Dehu, C., Meyers, F., Hendrickx. E.. Clays, K., Persoons, A., Marder, S.R., Bredas, J.L. Solvent effects on the second-order nonlinear optical response of tr-conjugated molecules A combined evaluation through self-consistent reaction field calculations and hyper-Rayleigh scaterring measurements. J. Am. Chem. Soc. 117, 10127-10128 (1995)... 

The understanding and reliable prediction of the influence of the solute-solvent interactions on the nonlinear optical properties of molecular systems is a significant issue for a width range of theoretical and experimental areas of studies. In this review, it was shown that the simple two-state approximations combined with tlie solvatochromic methods are an effective tools in prediction tlie direction of tlie changes of molecular nonlinear responses as a function of solvent polarity. This methodology based on the description of the solvent effects at the molecular level should be treated as a supporting for the most sophisticated quantum chemical approaches. 

Bogdan, E., Plaquet, A., Antonov, L., Rodriguez, V., Ducasse, L., Champagne, B., and Castet, F. (2010) Solvent effects on the second-order nonlinear optical responses in the keto-enol equilibrium of a 2-hydroxy-1-naphthaldehyde derivative. / Phys. Chem. C, 114, 12760-12768. 

This expression introduces the third order susceptibility of the medium, a quantity not easy to be accurately determined for the small portions of solvent in which the nonlinearity effect is sizeable. In addition we remark that with the favourable exception of atomic ions which have a spherical symmetry, the solvent layer in question has an irregular shape (not directly amenable to the molecular shape because the chemical groups responsible for nonlinearities are not regularly placed on the molecular surface). For this reason the whole tensorial expression of xCi> with a position dependent formulation, should be used. 

A simple but effective strategy ( corrected LR, or cLR) aimed at overcoming this intrinsic limit of the nonlinear effective solute Hamiltonian when applied to LR approaches has been first proposed by Caricato et al. [33], With such a strategy, the state-specific solvent response is recovered within the linear response approach. As a result, the LR-SS differences in vertical excitation energies are greatly reduced (still keeping the computational feasibility of LR schemes). 

K. Ando and S. Kato, Dielectric relaxation dynamics of water and methanol solutions associated with the ionization of /V,/V-dimcltiylanilinc theoretical analyses, J. Chem. Phys., 95 (1991) 5966-82 D. K. Phelps, M. J. Weaver and B. M. Ladanyi, Solvent dynamic effects in electron transfer molecular dynamics simulations of reactions in methanol, Chem. Phys., 176 (1993) 575-88 M. S. Skaf and B. M. Ladanyi, Molecular dynamics simulation of solvation dynamics in methanol-water mixtures, J. Phys. Chem., 100 (1996) 18258-68 D. Aheme, V. Tran and B. J. Schwartz, Nonlinear, nonpolar solvation dynamics in water the roles of elec-trostriction and solvent translation in the breakdown of linear response, J. Phys. Chem. B, 104 (2000) 5382-94. 

The nonlinear Smoluchowski-Vlasov equation is calculated to investigate nonlinear effects on solvation dynamics. While a linear response has been assumed for free energy in equilibrium solvent, the equation includes dynamical nonlinear terms. The solvent density function is expanded in terms of spherical harmonics for orientation of solvent molecules, and then only terms for =0 and 1, and m=0 are taken. The calculated results agree qualitatively with that obtained by many molecular dynamics simulations. In the long-term region, solvent relaxation for a change from a neutral solute to a charged one is slower than that obtained by the linearized equation. Further, in the model, the nonlinear terms lessen effects of acceleration by the translational diffusion on solvent relaxation. 

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