Quasi-universality in mixed counterions systems

TL;DR

This paper demonstrates that in systems with mixed counterions, the inter-plate pressure exhibits a quasi-universal behavior across different ionic compositions at comparable Coulombic couplings, challenging prior expectations of strong dependence on ionic mixture details.

Contribution

The study reveals that the equation of state for mixed counterion systems is quasi-universal at small distances, regardless of ionic composition, for similar Coulombic couplings.

Findings

Inter-plate pressure shows quasi-universality across different ionic mixtures.

Behavior is consistent at comparable Coulombic couplings.

Challenges the assumption of strong dependence on ionic mixture details.

Abstract

The screening of plate-plate interactions by counterions is an age-old problem. We revisit this classic question when counterions exhibit a distribution of charges. While it is expected that the long-distance regime of interactions is universal, the behaviour of the inter-plate pressure at smaller distances should a priori depend rather severely on the nature of the ionic mixture screening the plate charges. We show that is not the case, and that for comparable Coulombic couplings, different systems exhibit a quasi-universal equation of state.