Screening in Yukawa fluid mixtures

TL;DR

This paper investigates how the effective interactions between charged particles in a Yukawa fluid mixture are influenced by the solvent's correlation length and pair potentials, revealing conditions for screening and unscreening effects.

Contribution

It provides a theoretical analysis of screening phenomena in Yukawa fluid mixtures, clarifying when the effective potential is screened or unscreened based on solvent properties.

Findings

Yukawa interactions are screened if solvent pair potentials decay with the same screening length.

If solvent pair potentials are shorter ranged, the effective potential remains unscreened.

The screening behavior depends on the relative range of solvent and solute pair potentials.

Abstract

The effective pair potential between mesoscopic charged particles in a neutralising background medium takes a Yukawa form $\exp(-\lambda r)/r$ with screening length $\lambda^{-1}$. We consider a dilute suspension of such Yukawa particles dispersed in a solvent with correlation length $\xi<\lambda^{-1}$ and show that the Yukawa interaction is `screened' if the pair potentials between solvent particles exhibit Yukawa decay with the same screening length $\lambda^{-1}$. However, if the solvent pair potentials are shorter ranged than the solute Yukawa potentials, then the effective potential between pairs of solute particles is `unscreened', i.e. the effective potential between the solute particles is equal to the bare potential at large particle separations.