Sign change of hyperpolarizabilities of solvated water

Abstract

Articles you may be interested inSign change of the Soret coefficient of poly(ethylene oxide) in water/ethanol mixtures observed by thermal diffusion forced Rayleigh scattering Static hyperpolarizability of the water dimer and the interaction hyperpolarizability of two water molecules Absolute signs of hyperpolarizabilities in the liquid stateThe experimental work by Levine and Bethea ͓J. Chem. Phys. 65, 2429 ͑1976͔͒ and by Ward and Miller ͓Phys. Rev. A 19, 826 ͑1979͔͒ on the hyperpolarizability of solvated water and water in the gas phase, respectively, showed a very substantial effect of the solvent on the measured hyperpolarizability. The sign of the hyperpolarizability of solvated water changed compared to gas phase and the numerical value increased by a factor of 1.5. This article presents a theoretical investigation of the solvent effects of the hyperpolarizabilities and their frequency dispersions for liquid water using the continuum, semicontinuum, and supermolecular models. Calculations involving the semicontinuum and supermolecular models give the sign change of the hyperpolarizabilities, indicating that the hydrogen bonds and the static dipole interaction have substantial impact on the hyperpolarizability of liquid water. Hyperpolarizabilities calculated by the supermolecular approach are about one third of those calculated by the semi-continuum model. The continuum and semicontinuum models involve a recent implementation of a quantum mechanical reaction field response method.

Medium perturbations on the molecular polarizability calculated within a localized dipole interaction model

“…Experimental evidence 41,42 indicates that a tetrahedrally coordinated water molecule is present in liquid water and therefore we constructed a cluster containing the first solvation shell from Ref. 7. This tetrahedral structure has two donor hydrogen bonds and two acceptor hydrogen bonds ͑see Fig.…”

“…A simple alternative to the PPM model is the ''differential shell'' approach ͑DSA͒. 7,25 In DSA the solute polarizability is defined as the difference between the polarizability of the cluster and the polarizability of the solvent. Information about a specific member of the cluster can be obtained at the expense of one extra calculation.…”

“…These intermolecular effects can have significant influence on the ͑hyper͒ polarizabilities of the molecules. [5][6][7][8][9][10][11] The presence of a medium ͑solvent͒ will affect the molecule ͑solute͒ in two ways. First, the externally applied fields are modified and, second, there is an explicit solute-solvent interaction.…”

“…An alternative is a combination of the continuum model and supermolecular calculations, the so-called semicontinuum model. 7,17,18 Although the supermolecular methods are accurate ͑within the chosen model͒ the properties obtained are for the total supermolecule or cluster. Unless the molecular property of interest is additive the problem of partitioning the total response into local contributions remains.…”

“…The solute-solvent interactions are most commonly taken into account by adopting the so-called continuum model; see, e.g., Refs. 7,8,15, and 16. The greatest disadvantage of the continuum models is the neglect of the explicit microscopic structure of the solvent.…”