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Published on: December 14, 2017
Physical mechanism of δ-δ'-ε phase stability in plutonium
Chun-Mei Li1,2, Börje Johansson3,4,5, Levente Vitos3,4,6
1College of Physical Science and Technology, Shenyang Normal University, 110034, Shenyang, China. cmli@synu.edu.cn.
Abstract:
Based on first-principle calculations, we have systematically explored the nature of the elastic stability and the δ-δ'-ε phase transitions in pure Pu at high temperature. It is found that, both the electron-phonon coupling and the spin fluctuation effects tend to decrease the tetragonal elastic constant (C') of δ-Pu, accounting for its anomalous softening at high temperature. The lattice thermal expansion together with the electron-phonon coupling can stiffen C' of ε-Pu, promoting its mechanical stability at high temperature. The δ-ε transition is calculated to take place around 750-800 K, and is dominated by the phonon vibration. The δ' intermediate phase is realized around 750 K mainly because of the thermal spin fluctuation.
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