Static dielectric properties of dense ionic fluids

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.

Dependence of the dielectric constant of electrolyte solutions on ionic concentration: A microfield approach

“…It is interesting to note that the fitted parameter ε ms does not seem to follow a clear trend, e.g., within a series of alkali chloride. Recent studies have focused on development of a theory for the value of ε ms in ionic liquids [30,31]. Extension of such a theory to concentrated electrolyte solutions, and providing and recovery of the dependence of ionic orientational polarization upon ionic concentration is the subject of future work.…”

Microphase separation and the formation of ion conductivity channels in poly(ionic liquid)s: A coarse-grained molecular dynamics study

“…The random force η i acts on each bead independently and obeys the fluctuation-dissipation theorem η ik = 0, and η ik (t)η jl (t ) = 2ζk B Tδ ij δ kl δ(t t ), which ensures the influence of Gaussian white noise for particles i and j in the spatial directions k and l. The temperature is set to T = 2 /k B , and the Langevin equation is integrated via a velocity Verlet algorithm with a time step of δt = 0.01 τ with τ = σ(m/ ) 1/2 . Motivated by the work of Zarubin and Bier for molecular ionic liquids 62 in all simulations a constant particle packing fraction of…”

Characterizing the Magnitude and Structure-Dependence of Free Charge Density Gradients in Room-Temperature Ionic Liquids

“…The size and shape of the ions and the absence of a dielectric solvent prevents organized ion packing, with both factors contributing to the materials existing in the liquid phase under ambient conditions. There is a substantial body of work extant focusing on the bulk physical properties of RTILs, including efforts aimed at understanding the role of hydrogen bonding in mediating mobility, characterizing mass and charge transport, − determining dissociation, − dielectric response, − and issues associated with local and long-range electrostatic interactions. − RTILs hold promise for a variety of practical applications, including use as solvents for chemical separations , and syntheses, , as electrolytes for supercapacitors − and fuel cells, , and potentially as novel electro-optic materials . Despite the wide range of applications for RTILs, there remain many fundamental issues to be resolved, especially with regard to fluidity and ion dynamics, and with understanding the organization and response of these materials when subjected to external forces.…”