The Eyring Significant Structure Theory Applied to the Calculation of Surface Tension of Simple Liquids

Abstract

The study of surface tension is of immense importance and it has been intensively studied by experimental and theoretical scientists[1–4,5]. Several theories have been proposed for the surface tension of liquids. March and Tosi[1] have comprehensively reviewed various theoretical models. However, due to characteristics of the liquid state, i.e., the strong interaction of particles and their state of disorder, the theoretical analysis has lagged far behind theories of the gaseous and the crystalline states. The alternative procedure is the model approach, in which one visualizes a physical model of the liquid, translates the picture in the mathematical language, i.e., a partition function, and then calculates the properties of the liquid. Such a model is the Eyring’s Significant Structure theory[6]. The theory is based on the idea that the vapor is mirrored in the liquid as vacancies which transform solid-like into gas-like degrees of freedom. The usefulness of the model cannot be doubted. However, criticisms have been raised against the theory. One of the disadvantages is that it has not been derived from an exact partition function by any mathematically well-defined approximation, but is a result of intuition. But when properly formulated, such a model should be a useful description of what actually happens, as in fact it is. In this paper, Eyring’s significant structure theory with monolayer approximation [7] has been used to calculate the surface tension of simple liquids in the temperature range from triple point to the critical temperature. The calculations for neon, krypton and xenon have been done using Lennard-Jones potential and such results have not been reported earlier. A comparison of the calculated surface tension is made with the experimental and the reported values by Wu and Yan[5] using density functional theory.

These calculations were done while working as a guest scientist at the International Centre for Theoretical Physics, Trieste, Italy during the period from September 7 to October 26, 1985.