Jiang Jianhui, Lu Shuang, Ouyang Yulou, Chen Jie
Center for Phononics and Thermal Energy Science, China-EU Joint Lab for Nanophononics, MOE Key Laboratory of Advanced Micro-structured Materials, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China.
Nanomaterials (Basel). 2022 Aug 18;12(16):2854. doi: 10.3390/nano12162854.
The phonon Boltzmann transport equation combined with first-principles calculation has achieved great success in exploring the lattice thermal conductivity (κ) of various materials. However, the convergence of the predicted κ is a critical issue, leading to quite scattered results recorded in the literature, even for the same material. In this paper, we explore the origin for the convergence of thermal conductivity in two-dimensional (2D) materials. Two kinds of typical 2D materials, graphene and silicene, are studied, and the bulk silicon is also compared as a control system for a three-dimensional material. The effect of the cutoff radius (rc) in the third-order interatomic force constants on κ is studied for these three materials. It is found that that κ of these three materials exhibits diverse convergence behaviors with respect to rc, which coincides very well with the strength of hydrodynamic phonon transport. By further analyzing the phonon lifetime and scattering rates, we reveal that the dominance of the normal scattering process gives rise to the hydrodynamic phonon transport in both graphene and silicene, which results in long-range interaction and a large lifetime of low-frequency flexural acoustic phonons, while the same phenomenon is absent in bulk silicon. Our study highlights the importance of long-range interaction associated with hydrodynamic phonon transport in determining the thermal conductivity of 2D materials.
声子玻尔兹曼输运方程与第一性原理计算相结合，在探索各种材料的晶格热导率（κ）方面取得了巨大成功。然而，预测的κ的收敛性是一个关键问题，导致文献中记录的结果相当分散，即使对于相同的材料也是如此。在本文中，我们探讨了二维（2D）材料中热导率收敛的起源。研究了两种典型的二维材料，石墨烯和硅烯，并将体硅作为三维材料的对照体系进行了比较。研究了这三种材料中三阶原子间力常数的截止半径（rc）对κ的影响。结果发现，这三种材料的κ相对于rc表现出不同的收敛行为，这与流体动力学声子输运的强度非常吻合。通过进一步分析声子寿命和散射率，我们发现，在石墨烯和硅烯中，正常散射过程的主导地位导致了流体动力学声子输运，这导致了长程相互作用和低频弯曲声子的长寿命，而体硅中不存在相同的现象。我们的研究强调了与流体动力学声子输运相关的长程相互作用在确定二维材料热导率方面的重要性。
