14 - Thermodynamics of Solid-Fluid Interfaces

Abstract

Solid-fluid interfaces differ from fluid-fluid interfaces because a solid can be strained elastically. Surface area can change by stretching and by addition of new surface, each process giving rise to surface stress. Interfacial energy and adsorption can be referenced to the area of either the unstrained crystal surface or its actual strained surface. Interfacial free energy of crystal-fluid interfaces is anisotropic, consistent with crystal symmetry, and can be described by a vector field known as the ξ-vector; its normal component is the surface free energy and its tangential component measures the change of energy with surface orientation. A small crystal can acquire an equilibrium shape that has facets and missing orientations and minimizes its surface energy. This shape can be computed from the Wulff construction or the ξ-vector. A large crystal surface can develop facets to minimize its energy. We derive Herring’s formula for the equilibrium potential on a curved crystal surface.