氮弗伦克尔对形成对铀氮化物高温比热容的贡献
The contribution of nitrogen Frenkel-pair formation to the high-temperature heat capacity of uranium mononitride
AI总结：
研究通过分子动力学模拟探讨氮弗伦克尔对形成对铀氮化物比热容的影响，发现缺陷热容贡献达10 J/(mol·K)，解释了高温比热容的超线性行为。
摘要：
铀氮化物（UN）的高温比热容在~1700 K以上仍存在不确定性，由于测量和模型结果冲突。为评估内在缺陷形成对观察到的$C_P(T)$超线性行为的贡献，我们使用两种原子间势能函数进行了大规模分子动力学模拟，量化了1800-2600 K范围内氮扩散和弗伦克尔对数量。两种模型均显示阴离子迁移率增加，但Tseplyaev势能函数产生显著更大的弗伦克尔浓度，产生高达~10 J/(mol·K)的缺陷热容贡献。此缺陷驱动项与历史相关性和最近的从头计算结果中的曲率一致，表明氮亚晶格无序提供了一个合理的内在机制，解释了UN的高温比热容。
英文摘要：
The high-temperature heat capacity of uranium mononitride (UN) remains uncertain due to conflicting measurements and models above ~1700 K. To assess whether intrinsic defect formation contributes to the observed superlinear behavior of $C_P(T)$, we perform large-scale molecular dynamics simulations using two interatomic potentials to quantify nitrogen diffusion and Frenkel-pair populations from 1800--2600 K. Both models show increasing anion mobility, but the Tseplyaev potential yields substantially larger Frenkel concentrations, producing a defect heat-capacity contribution of up to ~10 J/(mol-K). This defect-driven term is consistent with the curvature seen in historical correlations and recent ab initio results, suggesting that nitrogen sublattice disorder provides a plausible intrinsic mechanism for the high-temperature heat capacity of UN.
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