UC Irvine

The actinide elements mark the emergence of 5f electrons. The f electrons possess sufficiently unuusual characteristics that their participation in atomic binding often results in dramatic changes in properties. This provides an excellent opportunity to study the question of localization of electrons; a question that is paramount in predicting the physical and chemical properties of d and f electron transition metals. The transition region between localized (magnetic) and itinerant (often superconducting) behavior provides for many interesting phenomena such as sctructural instabilities (polymorphism), spin fluctuations, mixed valences, charge density waves, exceptional catalyic activity and hydrogen storage. This region offers most interesting behavior such as that exhibited by the actinide compounds UBe13 and UPt3. Both compounds are heavy-fermion superconductors in which both magnetic and superconducting behavior exist in the same electrons. The consequences of f-electron bonding (which appears greatest at plutonium) show dramatic effects on phase stability, alloying behavior, phase transformations and mechanical behavior. © 1985.