单原子层薄膜热传导性质的晶格动力学研究(II)——数值计算与结果分析

Lattice Dynamics Study on the Thermal Conduction Properties of Single Atomic Layer Films (II)—Numerical Calculations and Analysis on the Results

摘要: 本文在先前得到公式的基础上，对单原子层薄膜晶格的声子线宽、声子自由程和声子对热传导系数贡献与其波矢的关系进行了计算，并计算了薄膜热膨胀系数随尺寸的变化规律。计算结果表明，短波矢声子即低频声子具有较长的自由程，对热传导系数的贡献较大。当薄膜尺寸增加时，声子自由程分布越往低波矢区域集中，并且低波矢区域的声子自由程越大，短波矢声子即低频声子对薄膜热传导系数的贡献越大。薄膜尺寸越大，热传导系数越大，并且当尺度N超过40个晶格常数时，其热传导系数与尺寸的对数logN之间存在线性关系，当尺寸趋于无穷时，热传导系数趋于发散，因此大尺寸单原子层薄膜有卓越的散热性能。

Abstract: Based on the formulas derived previously by the authors, the variation of the phonon line width, phonon free path, the contribution of phonon to thermal conductivity with its wave vector are calculated. The results show that the phonon with a shorter wave vector, or with a lower frequency, has a longer free path and a greater contribution to the thermal conductivity. When the size of the film increases, the more phonon free path distribution is concentrated in the low wave vector region, the phonon free path in the low wave vector region is larger, and the contribution of the short wave vector phonon, that is the low frequency phonon, to the thermal conductivity of the film is bigger. The larger the size of the film, the larger the thermal conductivity, and when the size N exceeds 40 lattice constants, there is a linear relationship between the thermal conductivity and logN. When the size tends to infinity, the thermal conductivity tends to diverge, so single atomic layer film with large size has excellent heat dissipation performance.