Sun Jie, Zhang Cunzhi, Yang Zhonghua, Shen Yiheng, Hu Ming, Wang Qian
School of Materials Science and Engineering, CAPT, HEDPS, BKL-MEMD, Peking University, Beijing 100871, China.
Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States.
ACS Appl Mater Interfaces. 2022 Mar 9;14(9):11493-11499. doi: 10.1021/acsami.1c24488. Epub 2022 Feb 22.
In recent years, increased attention has been paid to the study of four-phonon interactions and diffusion transport in three-dimensional (3D) thermoelectric materials because they play an essential role in understanding the thermal transport process. In this work, we study four-phonon scattering and diffusion transport in two-dimensional (2D) thermoelectric materials using the paraelectric phase of 2D SnSe as an example. The inherent soft phonon modes are treated by the self-consistent phonon theory, which considers the temperature-induced renormalization of the phonons. Based on density functional theory and the Peierls-Boltzmann transport equation for phonons, we show that the four-phonon interactions can reduce the thermal conductivity of the 2D SnSe sheet by nearly 40% due to the collapse of soft optical modes, and the contribution of diffusion transport to the total thermal conductivity accounts for 14% at a high temperature of 800 K due to the short phonon mean free path approaching the Ioffe-Regel limit, suggesting the two-channel transport in this system. The results are further confirmed by using the machine learning-assisted molecular dynamics simulations. This work provides a new insight into the physical mechanisms for thermal transport in 2D systems with strong anharmonic effects.
近年来，三维（3D）热电材料中的四声子相互作用和扩散输运研究受到了更多关注，因为它们在理解热输运过程中起着至关重要的作用。在这项工作中，我们以二维（2D）SnSe的顺电相为例，研究二维热电材料中的四声子散射和扩散输运。通过自洽声子理论处理固有软声子模式，该理论考虑了温度引起的声子重整化。基于密度泛函理论和声子的佩尔斯 - 玻尔兹曼输运方程，我们表明，由于软光学模式的崩塌，四声子相互作用可使二维SnSe薄片的热导率降低近40%，并且在800 K的高温下，由于声子平均自由程接近伊夫 - 雷格尔极限，扩散输运对总热导率的贡献占14%，这表明该系统中存在双通道输运。通过机器学习辅助分子动力学模拟进一步证实了这些结果。这项工作为具有强非谐效应的二维系统中的热输运物理机制提供了新的见解。
