Interface free energy or surface tension: definition and basic properties

TL;DR

This paper defines and explores the fundamental properties of interface free energy, also known as surface tension, using lattice models like the Ising model, highlighting its anisotropic nature and relation to phase equilibrium.

Contribution

It provides a first-principles definition of interface free energy and details its basic properties within lattice models, emphasizing anisotropy and relevance to crystal-vapor interfaces.

Findings

Interface free energy is anisotropic in lattice models.

The paper establishes a rigorous definition from statistical mechanics.

Results are applicable to crystal-vapor equilibrium scenarios.

Abstract

Interface free energy is the contribution to the free energy of a system due to the presence of an interface separating two coexisting phases at equilibrium. It is also called surface tension. The content of the paper is 1) the definition of the interface free energy from first principles of statistical mechanics; 2) a detailed exposition of its basic properties. We consider lattice models with short range interactions, like the Ising model. A nice feature of lattice models is that the interface free energy is anisotropic so that some results are pertinent to the case of a crystal in equilibrium with its vapor. The results of section 2 hold in full generality.