![\"plutonium\"](\"https:\/\/www.europesays.com\/uk\/wp-content\/uploads\/2025\/08\/plutonium.jpg\" "\\"Credit:")
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Credit: Pixabay\/CC0 Public Domain<\/p>\n
Normally, materials expand when heated. Higher temperatures cause atoms to vibrate, bounce around and take up a larger volume. However, for one specific phase of plutonium\u2014called delta-plutonium\u2014the opposite inexplicably occurs: it shrinks above room temperature.<\/p>\n
As part of its national security mission, Lawrence Livermore National Laboratory (LLNL) aims to predict the behavior of plutonium in all of its phases. Unraveling the mystery behind delta-plutonium’s abnormal behavior at high temperatures is an important piece of the picture.<\/p>\n
In a new study, published in Reports on Progress in Physics<\/a>, researchers from LLNL demonstrate a model that can reproduce and explain delta-plutonium’s thermal behavior and unusual properties. The model calculates the material’s free energy, a quantity that reflects the amount of available or useful energy in a system.<\/p>\n “Free energy fundamentally dictates the state of a material, so it is foundational for understanding it,” said LLNL scientist and author Per S\u00f6derlind. “An immense amount of effort at LLNL is dedicated to predicting the behavior of plutonium. The confidence in these predictions depends on a deep theoretical understanding of its electronic structure and free energy.”<\/p>\n Plutonium’s electronic structure is among the most complex of all elemental metals because its electrons are easily influenced by relativity, magnetism and crystal structure<\/a>. The new free-energy<\/a> model accounts for magnetic fluctuation effects for the first time.<\/p>\n “Our model is unique and novel because it includes magnetic states that are allowed to fluctuate and depend on temperature,” said S\u00f6derlind.<\/p>\n Acknowledging those magnetic states<\/a> in the theory causes it to match the odd experimental observations of contraction at high temperatures<\/a>.<\/p>\n This methodology could be extended to other materials where dynamic magnetism plays a role, such as iron and its alloys, which are important in geophysics. Going forward, the authors plan to address the impacts of microstructures, defects and imperfections that are present in real-world material.<\/p>\n More information:<\/strong> \n\t\t\t\t\t\t\t\t\t\t\t\t\tProvided by \t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/p>\n \n\t\t\t\t\t\t\t\t\t\t\t\tCitation<\/strong>: \n\t\t\t\t\t\t\t\t\t\t\t This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
\n\t\t\t\t\t\t\t\t\t\t\t\tPer S\u00f6derlind et al, First principles free energy model with dynamic magnetism for \u03b4-plutonium, Reports on Progress in Physics (2025). DOI: 10.1088\/1361-6633\/adedb1<\/a><\/p>\n
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tLawrence Livermore National Laboratory<\/a>
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\n\t\t\t\t\t\t\t\t\t\t\t\tNew model explains plutonium’s peculiar behavior (2025, August 6)
\n\t\t\t\t\t\t\t\t\t\t\t\tretrieved 6 August 2025
\n\t\t\t\t\t\t\t\t\t\t\t\tfrom https:\/\/phys.org\/news\/2025-08-plutonium-peculiar-behavior.html\n\t\t\t\t\t\t\t\t\t\t\t <\/p>\n
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