Application of the Lennard-Jones potential for calculating the surface tension and the formation enthalpy of a binary solution

Abstract

Abstract In our previous work on this topic, the Lennard-Jones potential was used to derive a semi-empirical formula relating the enthalpy of vaporization of a liquid to the density of the liquid and vapour at equilibrium with it, and a very good agreement between the formula and experimental data was demonstrated. In the present work, this approach has been further developed. The purpose of this work was to apply the Lennard-Jones potential to derive a semi-empirical formula describing the dependence of the surface tension of a liquid on temperature, as well as the dependence of the formation enthalpy of a binary solution on its composition. Solution formation was considered as consisting of two stages: 1) removal of x moles of the first component and 1– x moles of the second component from pure liquids into vacuum; in this case, the expended energy is equal to the energy of interaction of these molecules with all molecules in the volume of these liquids in accordance with the Lennard-Jones potential; 2) their movement from vacuum to an infinitely large volume of a solution of composition x; in this case, the released energy is equal to the energy of interaction of these molecules with all the molecules of the solution. The enthalpy of solution formation is equal to the algebraic sum of the mentioned interaction energies. Since surface tension is due to the action of the same forces of intermolecular interaction, a similar formula can be used to describe the dependence of surface tension on temperature. A comparison of the derived equations with the experiment shows that the resulting equations are in exceptionally good agreement with the experimental data.