Statistical mechanics of intermediate-valence rare earth compounds

Using thermodynamic perturbation theory the statistical mechanics of intermediate-valence rare earth compounds is investigated. The Gibbs' free energy is calculated to second order in the Anderson mixing interaction and is shown to diverge logarithmically as T tends to O. At high temperatures the susceptibility is approximately of the Curie-Weiss form chi = C/(T + Tsub(F), where kTsub(F) approximately Δ, the 'width parameter' associated with interconfigurational fluctuations. (author)