Qin Huasong, Ren Kai, Zhang Guoqiang, Dai Ying, Zhang Gang
Laboratory for Multiscale Mechanics and Medical Science, SV LAB, School of Aerospace, Xi'an Jiaotong University, Xi'an, 710049, China.
School of Mechanical and Electronic Engineering, Nanjing Forestry University, Nanjing, 210037, China.
Phys Chem Chem Phys. 2022 Aug 31;24(34):20437-20444. doi: 10.1039/d2cp01692c.
In this work, the heat transport properties of Janus MoSSe and WSSe monolayers are systematically investigated using non-equilibrium molecular dynamics simulations. Strong size dependence of the thermal conductivity is found in the Janus MoSSe and WSSe monolayers. In the two-dimensional limit, the Mo-based Janus MoSSe monolayer shows a higher thermal conductivity but similar phonon mean free path as MoS, while the W-based Janus WSSe monolayer shows a similar thermal conductivity but longer phonon mean free path than WSe. These two Janus monolayers also present quite different temperature dependencies. With temperature increasing from 100 K to 350 K, the reduction in thermal conductivity of MoSSe is up to 28.4%, but only 12.75% in WSSe, because of the weak temperature dependence in the phonon density of states. With 2% vacancy density, the thermal conductivity of defective MoSSe is only 16.03% that of pristine MoSSe, while for defective WSSe, the thermal conductivity is 14.04% that of pristine WSSe. The strong dependence on vacancy is explained by atomic heat flux vector analysis. The present study demonstrates rich physical phenomena in the thermal transport properties of Janus transition metal dichalcogenide monolayers, which may offer a new degree of freedom for manipulating their thermal conductivity for applications including thermal management and thermoelectric devices.
在这项工作中，使用非平衡分子动力学模拟系统地研究了Janus MoSSe和WSSe单层的热输运性质。在Janus MoSSe和WSSe单层中发现了热导率对尺寸的强烈依赖性。在二维极限下，基于Mo的Janus MoSSe单层表现出更高的热导率，但声子平均自由程与MoS相似，而基于W的Janus WSSe单层表现出相似的热导率，但声子平均自由程比WSe更长。这两种Janus单层还呈现出截然不同的温度依赖性。随着温度从100 K升高到350 K，MoSSe的热导率降低高达28.4%，而WSSe中仅为12.75%，这是由于声子态密度对温度的依赖性较弱。在空位密度为2%时，有缺陷的MoSSe的热导率仅为原始MoSSe的16.03%，而对于有缺陷的WSSe，热导率为原始WSSe的14.04%。通过原子热流矢量分析解释了对空位的强烈依赖性。本研究展示了Janus过渡金属二硫属化物单层热输运性质中丰富的物理现象，这可能为包括热管理和热电器件在内的应用中操纵其热导率提供一个新的自由度。
