The synthesis, storage, application, and disposal of various actinide materials in the fields of nuclear-fuel-based clean energy and actinide-metal-based metallurgy always closely correlate with the stabilities of U and Pu oxides in many atmospheric and aqueous environments. It is technologically important to jointly evaluate both the thermodynamic and electrochemical stabilities of actinide oxides there, for which free energy of formation (Δ_fG) is the key physical quantity. Due to various unavoidable technical and physical challenges in experiments, the Δ_fG data for these polyvalent oxides have long-standing inaccurate and incomplete problems. Here, we design an integrated first-principles approach to carry out efficient structural screenings, accurate energetic calculations by considering both the exact electronic potential and phononic contribution, and reliable mappings of the thermodynamic and electrochemical phase diagrams for anhydrous and hydrous actinide oxides in different environments (e.g., dry air, humid air, and aqueous solution). Based on the accurate and complete stability-composition-environment relationships constructed here, the established thermodynamic and electrochemical understandings can successfully explain versatile experimental observations on the hydration, oxidation, and corrosion behaviors of actinide oxides. Finally, the isotope effects on Δ_fG values are quantitatively predicted, revealing that any oxide will have nearly the same stability in environments with light and heavy waters. The systematically accurate electronic structure, thermodynamic stability, and electrochemical stability of actinide oxides as obtained in this work can provide many related theoretical and experimental studies in the future with reliable and desirable numerical references, as well as the comprehensively revealed physical and chemical mechanisms.

中文翻译：

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通过集成和准确的第一性原理计算绘制锕系氧化物的环境稳定性


核燃料清洁能源和锕系金属冶金领域中各种锕系材料的合成、储存、应用和处置始终与U和Pu氧化物在许多大气和水环境中的稳定性密切相关。联合评估锕系氧化物的热力学和电化学稳定性具有重要的技术意义，其中形成自由能（Δ _f G）是关键物理量。由于实验中不可避免的各种技术和物理挑战，这些多价氧化物的Δ _f G数据长期存在不准确和不完整的问题。在这里，我们设计了一种集成的第一性原理方法，通过考虑精确的电子势和声子贡献来进行有效的结构筛选、精确的能量计算，以及不同环境中无水和水合锕系氧化物的热力学和电化学相图的可靠映射（例如，干燥空气、潮湿空气和水溶液）。基于此处构建的准确且完整的稳定性-成分-环境关系，所建立的热力学和电化学理解可以成功解释锕系氧化物的水合、氧化和腐蚀行为的多种实验观察结果。最后，定量预测了同位素对 Δ _f G 值的影响，揭示了任何氧化物在轻水和重水环境中都具有几乎相同的稳定性。 本工作获得的锕系氧化物系统精确的电子结构、热力学稳定性和电化学稳定性可以为未来许多相关的理论和实验研究提供可靠和理想的数值参考，并全面揭示物理和化学机制。