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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.

No abstract

Canonical Monte Carlo (NVT-MC) simulations were performed to obtain surface tension and coexistence densities at the liquid-vapor interface of one-site associating Lennard-Jones and hard-core Yukawa fluids, as functions of association strength and temperature. The method to obtain the components of the pressure tensor from NVT-MC simulations was validated by comparing the equation of state of the associative hard sphere system with that coming from isothermal-isobaric Monte Carlo simulations. Surface tension of the associative Lennard-Jones fluid determined from NVT-MC is compared with previously reported results obtained by molecular dynamics simulations of a pseudomixture model of monomers and dimers. A good agreement was found between both methods. Values of surface tension of associative hard-core Yukawa fluids are presented here for the first time.