A second look at the cavity shape effect on the magnitude of the reversible work of cavity creation

Cavity creation is a fundamental process for theoretically describing and rationalizing several phenomena occurring in pure liquids and solutions. It has previously been shown that the shape of the cavity plays a pivotal role in determining the magnitude of the reversible work required to create it. The present study aims to provide a further and more in-depth analysis of this issue, by applying the analytical relations of classic Scaled Particle Theory to three different cavity shapes: spherical, prolate, and oblate spherocylindrical. The analysis shows that, regardless of the cavity shape, and in both water and carbon tetrachloride, a plateau (in particular, an asymptotic maximum) always appears in the curve describing the trend of the reversible work associated with the creation of cavities of increasingly larger size, per unit of solvent accessible surface area, with respect to the solvent accessible surface area of the cavity itself. The height of the plateau depends strongly on the cavity shape and shows no clear relationship with the liquid-vapour surface tension of the liquid. Furthermore, when considering both oblate and prolate spherocylindrical cavities possessing the same van der Waals volume as a given spherical cavity, the asymptotic maximum is present for oblate spherocylindrical cavities, whereas it becomes an asymptotic minimum for prolate spherocylindrical cavities, emphasizing the role played by the curvature of the cavity.