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Phase stabilization by electronic entropy in plutonium.

ABSTRACT: Plutonium metal undergoes an anomalously large 25% collapse in volume from its largest volume ? phase (?-Pu) to its low temperature ? phase, yet the underlying thermodynamic mechanism has largely remained a mystery. Here we use magnetostriction measurements to isolate a previously hidden yet substantial electronic contribution to the entropy of ?-Pu, which we show to be crucial for the stabilization of this phase. The entropy originates from two competing instabilities of the 5f-electron shell, which we show to drive the volume of Pu in opposing directions, depending on the temperature and volume. Using calorimetry measurements, we establish a robust thermodynamic connection between the two excitation energies, the atomic volume, and the previously reported excess entropy of ?-Pu at elevated temperatures.

SUBMITTER: Harrison N

PROVIDER: S-EPMC6639308 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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Phase stabilization by electronic entropy in plutonium.

Harrison N N Betts J B JB Wartenbe M R MR Balakirev F F FF Richmond S S Jaime M M Tobash P H PH

Nature communications 20190718 1

Plutonium metal undergoes an anomalously large 25% collapse in volume from its largest volume δ phase (δ-Pu) to its low temperature α phase, yet the underlying thermodynamic mechanism has largely remained a mystery. Here we use magnetostriction measurements to isolate a previously hidden yet substantial electronic contribution to the entropy of δ-Pu, which we show to be crucial for the stabilization of this phase. The entropy originates from two competing instabilities of the 5f-electron shell, ...[more]

PMID: 31320635

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