When is a material stable?

Abstract

This chapter is an introduction to classical thermodynamics that does not assume any knowledge of the subject. The significance of thermodynamic equilibrium in materials is discussed keeping in mind that it is rarely achieved in practice. The concepts of thermodynamic systems, components, work, energy, phase, absolute temperature, heat, potential energy, internal energy, state variables, intensive and extensive variables are introduced and defined. The first and second laws of thermodynamics are introduced. The concept of entropy is discussed in terms of irreversibility, the direction of time and microstates of the system. Configurational entropy is illustrated with the example of a binary alloy. The Helmholtz and Gibbs free energies are introduced and their physical significance is discussed in terms of the conditions for a material to be in equilibrium with its environment. This leads to a discussion of chemical potentials, the Gibbs-Duhem relation for each phase present and the phase rule.