The thermal conductivity (κ) of nonmetals is determined by the constituent atoms, the crystal structure and interatomic potentials. Although the group-IV elemental solids Si, Ge and diamond have been studied extensively, a detailed understanding of the connection between the fundamental features of their energy landscapes and their thermal transport properties is still lacking. Here, starting from first principles, we analyze those factors, including the atomic mass (m) and the second- (harmonic) and third-order (anharmonic) interatomic force constants (IFCs). Both the second- and third-order IFCs of Si and Ge are very similar, and thus Si and Ge represent ideal systems to understand how the atomic mass alone affects κ. Although the group velocity (v) decreases with increasing atomic mass (), the phonon lifetime (τ) follows the opposite trend (). Since the contribution to κ from each phonon mode is approximately proportional v ² τ, κ is lower for the heavier element, namely Ge. Although the extremely high thermal conductivity of diamond is often attributed to weak anharmonic scattering, the anharmonic component of the interatomic potential is not much weaker than those of Si and Ge, which seems to be overlooked in the literature. In fact, the absolute magnitude of the third-order IFCs is much larger in diamond, and the ratios of the third-order IFCs with respect to the second-order ones are comparable to those of Si and Ge. We also explain the experimentally measured κ of high-quality diamonds (Inyushikin etal 2018 Phys. Rev. B 97 144305) by introducing boundary scattering into the picture, and obtain good agreement between calculations and measurements.

非金属的热导率 ( κ ) 由组成原子、晶体结构和原子间势决定。尽管已经对 IV 族元素固体 Si、Ge 和金刚石进行了广泛的研究，但仍缺乏对其能量景观的基本特征与其热传输特性之间的联系的详细了解。在这里，从第一性原理开始，我们分析了这些因素，包括原子质量 ( m ) 和二阶（谐波）和三阶（非谐波）原子间力常数 (IFC)。Si 和 Ge 的二阶和三阶 IFC 非常相似，因此 Si 和 Ge 代表了理解原子质量如何单独影响κ 的理想系统。尽管群速度 (v ) 随着原子质量 ( ) 的增加而减小，声子寿命 ( τ ) 遵循相反的趋势 ( )。由于每个声子模式对κ的贡献近似成比例v ² τ，κ对于较重的元素，即 Ge，较低。虽然金刚石极高的热导率往往归因于弱非谐散射，但原子间势的非谐分量并不比硅和锗弱多少，这在文献中似乎被忽视了。事实上，金刚石中三阶 IFC 的绝对数量要大得多，三阶 IFC 与二阶 IFC 的比例与 Si 和 Ge 相当。我们还通过在图片中引入边界散射来解释实验测量的高质量钻石的κ (Inyushikin et al 2018 Phys. Rev. B 97 144305)，并在计算和测量之间获得良好的一致性。