Physicists have made incredible progress in decoding the strange atomic architecture of alpha plutonium. This difficult and fickle filament is well-known for its troublesome brittleness. Their collaboration between scientists at the Los Alamos National Laboratory and Brookhaven National Laboratory yielded thrilling new findings. Most importantly, they found that covalent bonds play a crucial role in determining alpha plutonium’s unique properties. This project highlights innovative experimental methods. Perhaps most importantly, it sets a precedent for future research and cooperation across different offices in the Department of Energy (DOE).
The investigation focused on how the presence of covalent bonding influences alpha plutonium’s behavior, particularly its brittleness as opposed to malleability. The team utilized the new Pair Distribution Function (PDF) beamline at the National Synchrotron Light Source II (NSLS-II) for their experiments. Through their research, they pushed each other artistically and creatively. This facility made it possible for researchers to utilize unique high-energy capabilities. They were able to go deep into thick samples of alpha plutonium, revealing never before seen information about its atomic structure.
Collaborative Research Efforts
To realize this ambitious study, experts from a wide variety of fields came together, showcasing the critical role interdisciplinary collaboration plays in scientific research. Milinda Abeykoon, the lead beamline scientist at Brookhaven’s NSLS-II, was an integral partner in making these experiments possible. Our co-lead authors Adam Phelan and Alexander Muñoz joined the project with unique and complementary skill sets. Adam on nuclear materials science and Alexander on computational physics, both from Los Alamos National Laboratory.
Phelan underlined the importance of knowing alpha plutonium’s mechanical properties to facilitate its use in future nuclear technologies. He noted that researchers often find themselves interested in these properties due to their implications for safety and performance in nuclear applications.
“In the field of plutonium, researchers are often interested in its mechanical properties for nuclear technology applications,” – W. Adam Phelan.
Abeykoon stressed the collaborative approaches used in the research, including Wide-Angle X-ray Scattering (WAXS) and Pair Distribution Function (PDF) techniques. WAXS returned information on long-range order and high-crystalline features, whereas PDF unveiled a deeply nuanced account of the local atomic environment.
“The model captured the long-range structural order of the first dataset remarkably well,” – Milinda Abeykoon.
Unraveling Complex Structures
Alpha plutonium poses an exceptional challenge to researchers as its highly complex structure produces a rich tapestry of information. Muñoz emphasized the richness and complexity of that data. This complexity makes it difficult to identify large-scale trends and develop hard conclusions.
“α-Pu is a particularly tricky system to study. Its structure is complex, which generates a lot of information,” – Alexander Muñoz.
As the team reported, their work revealed that the covalent bonding landscape in alpha plutonium agrees with theoretical predictions regarding Peierls distortion. This puzzling phenomenon happens as the material relaxes its crystal structure, making small shifts to its atomic positions, which serve to reduce the total energy. These observations explain how and why alpha plutonium behaves as a brittle solid. They explain why it doesn’t act like one of the most ductile metals on Earth.
Phelan reflected on the barriers encountered while conducting their investigation, citing a heavy computational burden needed to accurately investigate these rarities.
“You rarely get this bottom-up, atomistic understanding in plutonium science,” – W. Adam Phelan.
Implications for Future Research
This study significantly improves our understanding of alpha plutonium. It sets precedents for similar future cooperative research endeavors throughout the DOE complex. In it, the researchers explain how both covalent bonding and Peierls distortion function. This discovery has provided an invigorating new direction for science and research surrounding the mechanical properties and use cases of plutonium-based materials.
These efforts, Abeykoon noted, proved fruitful as they met their long-range order goals. What they found were these unanticipated changes in short-range atomic correlations. This finding adds additional complexity to the quest in understanding alpha plutonium’s structure and behavior.
“But the short-range atomic correlations revealed clear deviations from the expected pattern. That was exactly what we were expecting though,” – Milinda Abeykoon.
Phelan walked through the exhilarating, collaborative timeline that produced this surprise success. Kumarathasan contacted Abeykoon to discuss the experiment’s feasibility literally just hours before celebrating a personal milestone of his own—the birth of his child.
“I reached out to Milinda about the nature of the experiment and asked if it was feasible, and he sent back an encouraging reply two hours before my child was born,” – W. Adam Phelan.