Physics and Chemistry of Electrons and Ions in Condensed Matter : Springer : 9789027717993 : 9027717990 : 30 Sep 1984 : xvii PART I PROPERTIES OF CRYSTALLINE MATERIALS The Effective U in Oxides and in Sulfides: Conceptual Phase Diagrams and their Applications . . . . . . . . . . . . . . . ; . . . . . . . .. . . . . . . . 1 John B. Goodenough 1. Definitions 1 2. Interatomic interactions 23 References 44 Electron Correlations in Elementary Structures. The Case of Weak Correlations: Metallic and Covalent Bondings . . . . . . . . . . . . . . . . . 45 J. Friedel Introduct i on 45 1. The H2 molecule 46 2. Other elementary diatomic molecules 52 3. Metallic aggregates 53 4. Macroscopic phases of transition metals 57 5. Aggregates and solids of tetravalent (sp) elements 64 6. Aggregates of covalent dimers 67 7. Weak distortions of metallic closepacked or covalent structures 69 Appendixes 74 References 82 Statistical Thermodynamics of Mixed Valence at Low Temperatures . .. . . . . . . . . . . .