DFT study of the hexagonal high-entropy alloy fission product system

• Published in: Journal of nuclear materials 2017-05, Vol.488, p.70-74
• Main Authors: King, D.J.M., Burr, P.A., Obbard, E.G., Middleburgh, S.C.
• Format: Article
• Language: English
• Subjects: Alloys; Atomic structure; Atomic-scale simulations; Density functional theory; Density functional theory (DFT); DFT study; Ejection; Entropy; Fission products; High entropy alloys; High-entropy alloy; Metallic fission product; Metallic phase; Molybdenum; Nuclear fission; Operating temperature; Ordered structures; Order–disorder phenomena; Palladium; Rhodium; Ruthenium; Ruthenium alloys; Simulation; Single phase; Solid solutions; Stability; Technetium
• ISSN: 0022-3115; 1873-4820; 1873-4820
• DOI: 10.1016/j.jnucmat.2017.02.042

The metallic phase fission product containing Mo-Pd-Rh-Ru-Tc can be described as a hexagonal high-entropy alloy (HEA) and is thus investigated using atomic scale simulation techniques relevant to HEAs. Contrary to previous assumptions, the removal of Tc from the system to form the Mo-Pd-Rh-Ru analog is predicted to reduce the stability of the solid solution to the point that σ-Mo5Ru3 may precipitate out at typical fuel operating temperatures. The drive for segregation is attributed to the increased stability of the solid solution with the ejection of Mo and Ru. When Tc is included in the system, a single phase hexagonal solid solution is expected to form for a wider range of compositions. Furthermore, when cooled below 700 °C, this single phase solid solution is predicted to transition to a partially ordered structure. Future studies using the Tc-absent analogue will need to take these structural and chemical deliberations into consideration. [Display omitted]