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

• 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.

Ämnesord

NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

Nyckelord

Density functional theory (DFT)

High-entropy alloy

Metallic fission product

Order–disorder phenomena

Density functional theory

Entropy

Fission products

Molybdenum

Palladium

Rhodium

Ruthenium

Ruthenium alloys

Technetium

Atomic-scale simulations

DFT study

High entropy alloys

Metallic phase

Operating temperature

Ordered structures

Single phase

Solid solutions

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