SnSSe和SnS$_2$热电材料中的热输运：玻尔兹曼输运方程的非平衡蒙特卡罗模拟
Thermal transport in thermoelectric materials of SnSSe and SnS$_2$: a non-equilibrium Monte-Carlo simulation of Boltzmann transport equation
AI总结：
本研究通过非平衡蒙特卡罗模拟探究SnSSe和SnS₂的热输运特性，明确了声子贡献、温度演化规律及热电参数关系，指出最高温、温度梯度与塞贝克系数是筛选高效热电材料的关键。
摘要：
本研究采用声子玻尔兹曼方程的非平衡蒙特卡罗模拟方法，探究了Janus SnSSe和SnS$_2$这两种高效热电候选材料的热输运与能量转换特性。研究开展了声子分析以确定热输运中的贡献声子，结果显示主导热输运的声子为纵声学声子，贡献最小的则是横声学（TA）模。两种材料在施加废热后均达到了极高的最高温度，这归因于临界TA声子的占比较低。此外，研究还分析了材料加热和冷却过程中的温度分布，发现SnS$_2$中的热传播初始速度更快，导致其整体材料的温度梯度小于SnSSe。随着时间推移，与材料热导率直接相关的热传递速率会减慢，因此SnS$_2$和SnSSe的热传播状态会趋于相似。研究进一步明确了热电优值（zT）、效率（$η$）和生成电压的变化规律，指出更高的zT和$η$并不能保证产生更大的塞贝克电压——这是因为生成的塞贝克电压与热端和冷端结之间的温差相关，因此材料在施加废热后的温升幅度与所得电压直接相关。研究主要表明，材料所能达到的最高温度，连同温度梯度和材料的塞贝克系数特性，是筛选具有合理热电能量转换效率的高效热电材料的关键因素。
英文摘要：
In the present work, thermal transport and energy conversation in two thermoelectrically efficient candidates of Janus SnSSe and SnS$_2$ are investigated within the non-equilibrium Monte Carlo simulation of phonon Boltzmann equation. The phonon analysis is performed to determine the contributed phonons in heat transport. The results present that the dominant participating phonons are longitudinal acoustic ones while the least belongs to the transverse acoustic (TA) mode. Both materials reached the very high maximum temperature in response to the implied wasted heat. This is attributed to the low presence of the critical TA phonons. Also, the temperature profile achieved during the heating and cooling of the materials is studied. It is obtained that the heat propagation through the SnS$_2$ is, at first, swifter, which results in a temperature gradient through the whole material which is less than that of the SnSSe. As the time passes, the heat transfer that is directly related to the material thermal conductivity, slows down. So, the behavior of the SnS$_2$ and SnSSe, in case of the heat propagation status, becomes similar. More, the behavior of the thermoelectric figure of merit (zT), the efficiency ($η$), and the generated voltage have been figured out. It is stated that the higher zT and $η$ do not guarantee a larger generated Seebeck voltage. This is true, while the generated Seebeck voltage is related to the temperature difference between the heated and the cold junction. Accordingly, how far the temperature of matter rises in response to the implied wasted heat is related to the obtained voltage. Mainly, it is presented that the maximum temperature that a material achieves, alongside the temperature gradient and material property Seebeck coefficient, are essential in introducing thermoelectrically efficient materials with reasonable thermal to electrical energy conversion.
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