Static dielectric properties of dense ionic fluids

TL;DR

This study investigates the static dielectric properties of dense ionic fluids like RTILs and fused salts using Monte Carlo simulations, revealing scale-dependent screening and polarization behaviors that challenge simple electrolyte interpretations.

Contribution

A new scheme is developed to decompose dielectric susceptibility into orientation and distortion contributions across different length scales.

Findings

Long-range behavior shows plasma-like perfect screening.

Short-range behavior is dominated by orientation polarization.

RTILs may not be simply dilute electrolytes, depending on the scale considered.

Abstract

The static dielectric properties of dense ionic fluids, e.g., room temperature ionic liquids (RTILs) and inorganic fused salts, are investigated on different length scales by means of grandcanonical Monte Carlo simulations. A generally applicable scheme is developed which allows one to approximately decompose the electric susceptibility of dense ionic fluids into the orientation and the distortion polarization contribution. It is shown that at long range the well-known plasma-like perfect screening behavior occurs, which corresponds to a diverging distortion susceptibility, whereas at short range orientation polarization dominates, which coincides with that of a dipolar fluid of attached cation-anion pairs. This observation suggests that the recently debated interpretation of RTILs as dilute electrolyte solutions might not be simply a yes-no-question but it might depend on the considered length scale.