Abstract It is believed that the quasi-harmonic approximation can well describe the volume-dependent phonon frequency of most materials at zero temperature. In this work, we found that this widely used method cannot accurately describe the phonon frequencies of transition metals V and Nb at 0 GPa and 0 K. Therefore, the phonon-phonon interactions are further considered, and the phonon dispersion curves of V and Nb varying with temperature under zero pressure are derived. It is found that the calculated phonon dispersion curves of them at 300 K are in good agreement with the experimental results, indicating that the anharmonic effect is of great importance in the case of V and Nb. In addition, combined with the Boltzmann transport equation of phonons, the lattice thermal conductivity of V and Nb is also studied. The results show that the lattice thermal conductivity of V and Nb at 300 K is 4.35 and 9.87 Wm−1K−1, which are far lower than their electronic thermal conductivity at the same temperature, indicating that the electronic thermal conductivity of V and Nb is dominant at room temperature.

中文翻译：

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钒和铌在高温下的从头算动力学稳定性和晶格热导率

摘要 相信准谐波近似可以很好地描述零温度下大多数材料的体积相关声子频率。在这项工作中，我们发现这种广泛使用的方法不能准确描述过渡金属 V 和 Nb 在 0 GPa 和 0 K 下的声子频率。因此，进一步考虑了声子 - 声子相互作用，以及 V 和 Nb 的声子色散曲线导出在零压力下随温度变化。发现它们在 300 K 时的计算声子色散曲线与实验结果非常吻合，表明在 V 和 Nb 的情况下非谐效应非常重要。此外，结合声子的玻尔兹曼输运方程，还研究了V和Nb的晶格热导率。