A Proposed Catalytic Mechanism of Pd on the Formation of UBe13 in Experimental Construction of U-PD Phase Diagrams

Abstract

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, UBe₁₃, 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 UBe₁₃ 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.