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<p>In addition to being the most used nuclear fuel, uranium dioxide is a superionic conductor like some battery materials, for which molecular dynamic calculations evidenced string-like collective motion that exists in glass forming materials. Its simple crystalline structure and the development of up to date dedicated modeling makes UO<sub>2</sub> a prototypical material for the study of anharmonic dynamic that lies underneath its specific properties. In this paper, the analysis of two specific phonons modes by empirical potential calculation led us to the identification of UO<sub>2</sub> high temperature phase transition as Fm-3m to Pa-3 first order transition. We propose that the dynamic coexistence of these two phases at high temperature could be an explanation for string-like motion. The prediction made by calculations of a phase transition in UO<sub>2</sub> questions its existence in other surperionic compounds having fluorite structure, and the manner by which it can be confirmed both theoretically and experimentally.</p>

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Empirical potential calculations of UO2 for a better understanding of its stringlike motion at high temperature

  • 期刊论文

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  • 发表日期：

    2025年3月6日

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  • L.Desgranges

摘要

In addition to being the most used nuclear fuel, uranium dioxide is a superionic conductor like some battery materials, for which molecular dynamic calculations evidenced string-like collective motion that exists in glass forming materials. Its simple crystalline structure and the development of up to date dedicated modeling makes UO2 a prototypical material for the study of anharmonic dynamic that lies underneath its specific properties. In this paper, the analysis of two specific phonons modes by empirical potential calculation led us to the identification of UO2 high temperature phase transition as Fm-3m to Pa-3 first order transition. We propose that the dynamic coexistence of these two phases at high temperature could be an explanation for string-like motion. The prediction made by calculations of a phase transition in UO2 questions its existence in other surperionic compounds having fluorite structure, and the manner by which it can be confirmed both theoretically and experimentally.