AVS 57th International Symposium & Exhibition
    Actinides and Rare Earths Topical Conference Tuesday Sessions
       Session AC-TuA

Paper AC-TuA7
Elastic Moduli of Pure Alpha, Beta, Gamma Plutonium—Three Different Metals

Tuesday, October 19, 2010, 4:00 pm, Room Isleta

Session: Science and Technology of Actinides and Rare Earths
Presenter: A. Migliori, Los Alamos National Laboratory
Correspondent: Click to Email
From 10 K to 580K plutonium changes phase from monoclinic alpha to body centered monoclinic beta to orthorhombic gamma structures. Each crystal structure is rare or unique for an elemental metal. Measurements presented here provide the first high-accuracy values for a single high-purity specimen of the elastic moduli of unalloyed polycrystal plutonium as a function of temperature throughout the entire range of existence of the alpha, beta, and gamma phases. The bulk and shear moduli, essential thermodynamic material properties, reflect important and huge changes with temperature, such that these phases present as three different metals. Unlike phase transformations in many other elements where the bonding, nearest-neighbor distances, and physical properties are closely related among phases, in the three lowest-temperature phases of plutonium, the relationships are missing, and support the extreme sensitivity of plutonium properties to phase, temperature, and almost-certainly, electronic structure. We describe here the characteristics and implications of these newly-observed properties.