Convexity of Thermodynamic Potentials
摘要
Whether a thermodynamic potential is “convex upward” or “convex downward” is often important in thermodynamics. In this chapter, we discuss this issue. The topics are the convexities of entropy S[U, V, N], internal energy U[S, V, N], enthalpy H[p; S, N], Helmholtz free energy F[T; V, N], and Gibbs free energy G[T, p; N], Legendre transformation, the concept of natural variables, phase, Gibbs’ phase rule, Duhem’s theorem, and the method to specify the thermodynamic state of a fluid particle.