Thermal and structural properties of ionic fluids

Abstract

The electrostatic interaction in ionic fluids is well-known to give rise to a characteristic phase behavior and structure. Sometimes its long range is proposed to single out the electrostatic potential over other interactions with shorter ranges. Here the importance of the range for the phase behavior and the structure of ionic fluids is investigated by means of grandcanonical Monte Carlo simulations of the lattice restricted primitive model (LRPM). The long-ranged electrostatic interaction is compared to various types of short-ranged potentials obtained by sharp and/or smooth cut-off schemes. Sharply cut off electrostatic potentials are found to lead to a strong dependence of the phase behavior and the structure on the cut-off radius. However, when combined with a suitable additional smooth cut-off, the short-ranged LRPM is found to exhibit quantitatively the same phase behavior and structure as the conventional long-ranged LRPM. Moreover, the Stillinger-Lovett perfect screening property, which is well-known to be generated by the long-ranged electrostatic potential, is also fulfilled by short-ranged LRPMs with smooth cut-offs. By showing that the characteristic phase behavior and structure of ionic fluids can also be found in systems with short-ranged potentials, one can conclude that the decisive property of the electrostatic potential in ionic fluids is not the long range but rather the valency dependence.

Smectic phases in ionic liquid crystals

“…However, the solution obtained from the modified one-particle direct correlation functionc (1) (r r r, ω ω ω, [̺]) exhibits the same functional form as the exact solution in Eq. (19), but with modified coefficients A i and B i (see the last paragraph in Appendix A).…”

“…(8), which indeed exhibits the generic form given by Eq. (19). Note, that concerning the bulk phases the Heaviside step function Θ(d/2 − |z − z ′ |) acts only as to confine the spatial integration domain to a single periodic cell, but does not generate a further dependence on the position z, because the bulk phases are considered to have a periodic structure only.…”

“…Thus, this solution has the same functional form as Eq. (19). (11)) and the solution obtained from the modified one-particle direct correlation functionc (1) given by Eq.…”

Lattice Model of an Ionic Liquid at an Electrified Interface

“…We will perform both MC simulations of a continuum ionic liquid and of its lattice counterpart. [68][69][70][71] Unfortunately, due to low move acceptance rates, continuum MC simulations can only be performed for sufficiently low ionic couplings and volume fractions, which are not realistic for ionic liquids. On the other hand, the Coulomb lattice gas model can be relaxed to equilibrium even for parameters appropriate for real ionic liquids.…”

Phase diagram of a bulk 1d lattice Coulomb gas

“…The lattice version of this model (LRPM) implements the steric exclusion by allowing at most one ion per site. Its phase diagram has the same structure as its continuous counterpart, but also exhibits significant differences stemming from the fact that the lattice facilitates organization [20][21][22][23][24][25][26][27][28][29]. The bulk properties of RPM and LRPM are thus well understood, but the link with the peculiar behaviour of an ionic liquid capacitor remains to be made.…”