Density anomaly of charged hard spheres of different diameters in a mixture with core-softened model solvent. Monte Carlo simulation results

Hribar-Lee Hribar-Lee

doi:10.5488/cmp.16.43607

Abstract

Very recently the effect of equisized charged hard sphere solutes in a mixture with core-softened fluid model on the structural and thermodynamic anomalies of the system has been explored in detail by using Monte Carlo simulations and integral equations theory [J. Chem. Phys., 2012, 137, 244502]. Our objective of the present short work is to complement this study by considering univalent ions of unequal diameters in a mixture with the same soft-core fluid model. Specifically, we are interested in the analysis of changes of the temperature of maximum density (TMD) lines with ion concentration for three model salt solutes, namely sodium chloride, potassium chloride and rubidium chloride models. We resort to Monte Carlo simulations for this purpose. Our discussion also involves the dependences of the pair contribution to excess entropy and of constant volume heat capacity on the temperature of maximum density line. Some examples of the microscopic structure of mixtures in question in terms of pair distribution functions are given in addition.

Highlights

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One can construct the temperature of maximum density line at this particular ion concentration, Ü ÓÒ 1⁄4o1⁄2
We perform a series of calculations to construct the temperature of maximum density (TMD) lines for different Ü, ÓÒ up to Ü ÓÒ 1⁄4o¿

Summary

Introduction

If one considers the model at Ü ÓÒ 1⁄4o¿ at a point of the TMD line with slightly higher total density but substantially lower temperature (figure 3) compared to the case described, the inter-ion electrostatic correlations are expected to be stronger. A quantitative cumulative measure of the distribution of particles of different species is commonly given in terms of the pair contribution to the excess internal energy per particle as a function of the total density for different compositions of the mixture and at different reduced temperatures.

Objectives

Results

Conclusion