Abstract We investigated the heat capacity and thermal conductivity of UN using first principles methods. The generalized gradient approximation (GGA) of the Perdew, Burke, and Ernzerhof functional, developed for solids (/PBEsol) as implemented in Quantum ESPRESSO (QE) and associated codes (EPW, Boltztrap, ShengBTE), was used. We evaluated the energy of the UN to be lower for ferromagnetic ordering than non-magnetic. We found, using QE code, that the lattice constant calculated using PBEsol functional and norm-conserving pseudopotentials is slightly larger for ferromagnetic UN (0.497 nm) than non-magnetic UN (0.489 nm) and they agree with experiment. We noted a significant contribution from the optical phonons to the lattice thermal conductivity, which was previously observed experimentally for urania. The phonons' calculated contribution to the thermal conductivity, which decreases with temperature, is smaller at room temperature (7.20 Wm−1K−1) than evaluated from the correlation recommended for urania (8.79 Wm−1K−1). However, urania's thermal conductivity deteriorates faster with temperature; therefore it becomes lower than that calculated for UN for temperatures higher than 490 K. The total thermal conductivity, evaluated here, leads to the total thermal conductivity of UN being overestimated below 1000 K. Therefore, further investigations are needed to evaluate the effect of the interaction of magnetic moments on uranium with phonons and electrons. Furthermore, the electronic thermal conductivity can only be performed for non-magnetic UN, using EPW and Boltztrap codes. The results are dependent on a selection of electronic carriers but show good qualitative agreement with experiment at higher temperatures. The calculated electrical resistivity of the UN at low temperature is much lower than measured, but is similar to the experimentally measured behaviour of non-magnetic ThN. On the other hand, Ziman's model predicts two orders of magnitude lower resistivity than presently calculated, which is in strong disagreement with the measured resistivity of UN, but compares well with the resistivity of aluminum.

中文翻译：

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一氮化铀热输运的第一性原理研究

摘要 我们使用第一性原理方法研究了 UN 的热容量和热导率。使用 Perdew、Burke 和 Ernzerhof 泛函的广义​​梯度近似 (GGA)，为固体 (/PBEsol) 开发，如在 Quantum ESPRESSO (QE) 和相关代码（EPW、Boltztrap、ShengBTE）中实施。我们评估了铁磁排序的联合国能量低于非磁性排序。我们发现，使用 QE 代码，使用 PBEsol 函数和范数守恒赝势计算的晶格常数对于铁磁 UN (0.497 nm) 比非磁性 UN (0.489 nm) 略大，并且他们与实验一致。我们注意到光学声子对晶格热导率的显着贡献，这在之前已通过铀的实验观察到。声子的 计算得出的热导率随温度下降，在室温下 (7.20 Wm-1K-1) 小于根据推荐用于铀的相关性评估 (8.79 Wm-1K-1)。然而，铀的热导率随温度下降得更快；因此，当温度高于 490 K 时，它变得低于 UN 的计算值。此处评估的总热导率导致 UN 的总热导率在 1000 K 以下被高估。因此，需要进一步调查以评估铀上的磁矩与声子和电子的相互作用。此外，电子热导率只能用于非磁性 UN，使用 EPW 和 Boltztrap 代码。结果取决于电子载体的选择，但在较高温度下与实验显示出良好的定性一致性。UN 在低温下的计算电阻率远低于测量值，但与非磁性 ThN 的实验测量行为相似。另一方面，Ziman 的模型预测电阻率比目前计算的低两个数量级，这与测量的 UN 电阻率有很大的不同，但与铝的电阻率相比却很好。