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首页> 外文期刊>Physical review >Hidden disorder in the α'→δ transformation of Pu-1.9 at. % Ga
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Hidden disorder in the α'→δ transformation of Pu-1.9 at. % Ga

机译：Pu-1.9 at的α'→δ转化中的隐患。镓百分比

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摘要

Enthalpy and entropy are thermodynamic quantities critical to determining how and at what temperature a phase transition occurs. At a phase transition, the enthalpy and temperature-weighted entropy differences between two phases are equal (ΔH = TΔS), but there are materials where this balance has not been experimentally or theoretically realized, leading to the idea of hidden order and disorder. In a Pu-1.9 at. % Ga alloy, the δ phase is retained as a metastable state at room temperature, but at low temperatures, the δ phase yields to a mixed-phase microstructure of δ- and α'-Pu. The previously measured sources of entropy associated with the α'→δ transformation fail to sum to the entropy predicted theoretically. We report an experimental measurement of the entropy of the α'→δ transformation that corroborates the theoretical prediction, and implies that only about 65% of the entropy stabilizing the δ phase is accounted for, leaving a missing entropy of about 0.5 k_B/atom. Some previously proposed mechanisms for generating entropy are discussed, but none seem capable of providing the necessary disorder to stabilize the δ phase. This hidden disorder represents multiple accessible states per atom within the δ phase of Pu that may not be included in our current understanding of the properties and phase stability of δ-Pu.
机译：焓和熵是热力学量，对于确定相变如何以及在什么温度下发生至关重要。在相变时，两相之间的焓和温度加权熵差相等（ΔH=TΔS），但是有些材料在实验或理论上尚未实现这种平衡，从而导致了隐藏顺序和无序的想法。在Pu-1.9 at。在Ga合金中，δ相在室温下保持为亚稳态，但在低温下，δ相产生δ-和α'-Pu的混合相微观结构。先前测量的与α'→δ转换相关的熵源无法归结为理论上预测的熵。我们报告了实验测量的α'→δ转换的熵，这证实了理论预测，并暗示仅占稳定δ相的熵的约65％被保留，而缺少约0.5 k_B /原子的熵。讨论了一些先前提出的产生熵的机制，但是似乎没有一个机制能够提供必要的无序来稳定δ相。这种隐藏的无序状态表示Pu的δ相中每个原子有多个可访问状态，这可能不包括在我们目前对δ-Pu的性质和相稳定性的理解中。

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  • 来源
    《Physical review》 |2012年第22期|p.224104.1-224104.5|共5页
  • 作者

    J. R. Jeffries; M. E. Manley; M. A. Wall; K. J. M. Blobaum; A. J. Schwartz;

  • 作者单位

    Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA;

    Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA;

    Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA;

    Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA;

    Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA;

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