Phase equilibria, thermodynamics, and crystal structures for the Pu--Pt--Rh system

Phase diagrams and thermodynamic properties for the Pu-Pt, Pu-Rh, and Pu-Pt-Rh systems were determined for the regions of high platinum and rhodium. A new phase, PuPt4, was discovered; three polymorphic transitions were associated with the PuPt3 phase; and crystal structures were determined for the PuPt5 and PuPt4 phases and the intermediate PuPt3 polymorph. Sublimation behavior and thermodynamic properties of selected Pu-Pt and Pu-Rh phases were determined by target collection and mass spectrometry. Dissociation to the elements was the predominant sublimation reaction up to 18000C. The high thermodynamic stability of these phases was analyzed in terms of the electronic configurations of the constituent elements