An ab initio analysis of medium perturbation on molecular polarizabilities

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Abstract
The effect of medium perturbation on the polarizabilities of solute molecules in condensed environment are evaluated and analyzed. Some solutes, including Ne, Ar, CH4, Cl−, and H2O, in liquid water and argon were treated employing a supermolecule approach with Monte Carlo simulations and ab initio molecular orbital calculations explicitly considering the solvent molecules. Dielectric solute–solvent interaction was calibrated to derive the intrinsic polarizabilities of solutes. The results revealed a general tendency of decrease in the polarizabilities in solutions from the vacuum values, as much as 13%–18% for neutral solute species and 37% for Cl− in water. The tendency was moderate in liquid argon, 1%–9% reduction for neutral species and 18% for Cl−. About a half of the reduction was attributed to the solute–solvent exchange interaction. Those results are not renormalized with the medium polarization, and thus suitable to model the intermolecular interactions in liquids.