Criticality in charge-asymmetric hard-sphere ionic fluids

Abstract

Phase separation and criticality are analyzed in z:1 charge-asymmetric ionic fluids of equisized hard spheres by generalizing the Debye-Hückel approach combined with ionic association, cluster solvation by charged ions, and hard-core interactions, following lines developed by Fisher and Levin for the 1:1 case (i.e., the restricted primitive model). Explicit analytical calculations for 2:1 and 3:1 systems account for ionic association into dimers, trimers, and tetramers and subsequent multipolar cluster solvation. The reduced critical temperatures, Tc* (normalized by z), decrease with charge asymmetry, while the critical densities increase rapidly with . The results compare favorably with simulations and represent a distinct improvement over all current theories such as the mean spherical approximation, symmetric Poisson-Boltzmann theory, etc. For z not equal to 1, the interphase Galvani (or absolute electrostatic) potential difference, Deltaphi(T), between coexisting liquid and vapor phases is calculated and found to vanish as absolute value (T-Tc) beta when T-->Tc-with, since our approximations are classical, beta = (1/2). Above Tc, the compressibility maxima and so-called k-inflection loci (which aid the fast and accurate determination of the critical parameters) are found to exhibit a strong z dependence.

Thermo-molecular orientation effects in fluids of dipolar dumbbells

“…Studying this system provides a way of bridging the gap between our previous work on nonpolar dumbbells and more complex realistic systems such as water. Dipolar dumbbells are interesting models in their own right, as simple but realistic approximations to real molecules such as carbon monoxide, or ionic salts at high temperature and low density which tend to form dimers [9][10][11][12], and this study contributes to the body of work already existing on the behaviour of these systems [13][14][15][16][17]. In particular, we are unaware of any other computer simulation studies of size-asymmetric dipolar dumbbells (but see Ref.…”

Plasma Polarization in High Gravity Astrophysical Objects

“…The second type of discussed polarization is also part of more general phenomenon (see for example [1]): (B) -any non-uniformity in equilibrium Coulomb system is accompanied by its polarization and existence of stationary profile of average electrostatic potential. Important particular case of this type of plasma polarization is existence of stationary drop of average electrostatic potential (Galvani potential) at any two-phase interface in equilibrium Coulomb system [2] (see also [1][2][3][4][5][6][7][8][9][10]). Plasma polarization at micro-level is well known in classical case as Debye-Hueckel screening [15] and in the case of degenerated electrons as Thomas-Fermi screening [16].…”

Ionic fluids: charge and density correlations near gas–liquid criticality

“…Due to the controversial experimental findings, the critical behavior of the RPM has also been under active debates and strong evidence for an Ising universal class has been found by computer simulation [7,8] as well as by a recent theoretical study [9]. More recently, the effects of size-and/or charge-asymmetry on the phase diagram have been studied theoretically [10]- [12] and by simulation [15,16].…”