An analytical equation of state for the hard core Yukawa fluid; the electroneutral mixture

Abstract

An explicit analytical equation of state is presented for an electroneutral fluid mixture of equal-sized particles which interact via hard core Yukawa potentials. Based on a perturbative scheme, analytical expressions for the coefficients of an inverse temperature expansion of internal energy in the mean-spherical approximation (MSA) are given. Extending an approximate procedure used recently for the one-component hard core Yukawa fluid, closed analytical mathematical expressions for the thermodynamics and equation of state of the electroneutral mixture are obtained. Thermodynamic properties and phase diagrams are studied for the symmetrical binary mixture. Results calculated with the analytical formulas presented here are compared with MSA results and shows excellent agreement when the interaction potential is short range. Two different binary systems are represented with the model studied in this work. In the first the interaction between particles of one species is given by repulsive Yukawa tails and the interaction between particles of different species by attractive Yukawa tails. The second system is obtained when all these forces are reversed.

Liquid-gas separation in colloidal electrolytes

“…10 These results also agree qualitatively with previous calculations for an attractive-repulsive mixture of Yukawa potentials using an expansion of the internal energy and the equation of state, based on the mean-spherical approximation ͑MSA͒. 24 As in the ionic fluids, the demixing in a dense and a dilute phase is driven by the strong correlations between oppositely charged particles. 1,14 We have investigated the internal correlations in two supercritical ͑T * = 0.18͒ states, * = 0.6 and * = 0.05, marked in Fig.…”

“…The internal energy calculated using the MSA for a mixture of Yukawa potentials shows similar trends, with minima moving to higher as the density increases. 24 …”

Surface tension at the liquid-vapor interface of screened ionic mixtures

“…The liquid-vapor equilibrium of YRPM has been studied by the mean spherical approximation (MSA) equation [8,13]. One of the main conclusions obtained in those works is that the critical temperature (T c ) increases and has a maximum as the potential decreases its range of interaction.…”

“…The Yukawa model with a hard-core repulsive interaction has been very useful in obtaining thermodynamic properties of one component and mixtures of charged particles using integral equations theory [7,8,12,13]. The liquid-vapor equilibrium of YRPM has been studied by the mean spherical approximation (MSA) equation [8,13].…”

“…Examples of these systems are colloidal suspensions of charged particles, electrolyte solutions and molten salts. The Restricted Primitive Model (RPM) has been the starting point to describe properties of charged particles using theory and simulation methods [7,8]. The interaction between particles in RPM is purely electrostatic and its range cannot be modified.…”