ABSTRACT
In 1878, Gibbs [1] published his celebrated “Theory of Capillarity,” the standard reference of surface thermodynamics ever since. In a rather compact-yet exhaustive and profound-manner, Gibbs treated fluid-fluid, as well as solid-fluid, interfaces and their equilibrium properties while representing the interfacial region in an Euclidean manner by a single dividing interface, preferably the so-called surface of tension. For this particular dividing surface, the standard Laplace (or Young-Laplace) equation [2]:
∆P=2Hγ (1)
holds exactly for a majority of cases. Here H=(c1+c2)/2 denotes the mean curvature, γ is the interfacial tension, and ∆P is the pressure jump at the interface, and c1 and c2 are the principal curvatures of the surface of tension. Moreover, for any given interface, the interfacial tension γ attains a minimum value when the surface of tension is chosen to be the dividing surface, as may readily be verified.
