A PROPOSED CATALYTIC MECHANISM OF Pd ON THE FORMATION OF UBe_(13) IN EXPERIMENTAL CONSTRUCTION OF U-Pd PHASE DIAGRAMS

摘要

In previous U-Pd phase diagram determinations, contamination reactions of berrylia crucibles were observed. Measures were taken to reduce the amount of beryllium in the samples; however, the possibility of formation of a very stable metallic compound, UBe_(13), was neglected. The measured U-rich side eutectic temperature and composition and the Pd-rich side liquidus were controversial and much higher than the calculated results. Thermodynamic evaluation shows that crucible contamination (the formation of UBe_(13) catalyzed by Pd) changed the system from a binary to a ternary one and made the identification of compounds and determinations of phase boundaries extremely difficult. By comparing the binary phase diagrams of U-transition metals around Pd, and using the results of Local Density Approximation and the contamination reaction identified in this paper, a possible catalytic mechanism of Pd in the metallic system is proposed.