Session P20 - Structural Phase Transitions.
MIXED session, Wednesday afternoon, March 22
208A, MCC
We have investigated the nature of structural phase transitions in elemental plutonium, focusing on the role of a novel, self-induced Anderson localization [1]. Our picture conceptually explains the unusual sequential phase transitions and anomalously low melting point. The basic premise of the model is the existence of an entropy-driven transition from a uniformly delocalized phase to one characterized by a disordered distribution of two kinds of atomic sites associated, with equal probability, with either localized or delocalized 5f electrons. This locally fluctuating site behavior is due to the singlet 5f component of the two electron atomic ground state, which is randomly driven by hybridization to itinerancy. The significance of two electron dynamics and the existence of the Anderson localization were established earlier in uranium-based systems. The applicability of this picture to plutonium is examined with an LDA-LMTO approach. Progress in this direction, and in predicting relevant material properties from ab-initio computation will be presented. [1] B. R. Cooper et al, Phil. Mag. B 79, 683 (1999).