Non-local dielectric response of a polar solvent and Debye screening in ionic solution

Abstract

The effect of spatial correlation in the solvent polarization fluctuations (‘solvent structure’) on the character of screening in an electrolyte solution is discussed. It is considerable when the typical wavenumbers of the solvent-permittivity spatial dispersion are comparable with the inverse Debye-screening length. The screening then is not described by a simple Debye exponent, in contrast to the results of Radić and Marčelja. Their conclusions concerning the effective enhancement of the Debye screening length is shown to be generally incorrect, being appropriate only in the limit of small ionic concentration, when the effect leads to a small correction to the normal Debye value.