Surface Energy: Definitions and Applications

This lecture covers the definitions of surface energy and interfacial energy, as well as the Wulff Plot. The instructor explains the concept of surfaces, interfaces, and their topological defects. Various definitions of surface energy are discussed, including the free energy needed to create a surface of unit area. The lecture also explores the relationship between surface stress and excess surface free energy, emphasizing the thermodynamics of the problem. Additionally, the equilibrium shape of materials of finite dimensions and the temperature dependence of excess surface free energy are addressed. The Wulff Construction and Wulf Plot are introduced to understand the equilibrium shape of materials. Key questions about different crystallographic planes having varying surface energies are also discussed.