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Heat conduction of inhomogeneous solid material: phonon analysis and application to thin films

非均匀固体材料的热传导：声子分析及其在薄膜中的应用

基本信息

批准号：
12650203
负责人：
MATSUMOTO Mitsuhiro
金额：
$ 2.56万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650203/
关键词：
Heat conduction of solids Lattice vibration analysis Phonon dynamics Wavelet analysis Molecular simulation Thin film devices フォノン分子動力学接触熱抵抗

项目摘要

We have developed a novel numerical technique of lattice vibration analysis in order to study the lifetime and the mean free path of vibration in solids for the purpose of investigating thermal conductivity of non-metallic solids. This technique utilizes a wavelet transformation to analyze time-sequential or spatial data of atomic positions obtained with molecular dynamics simulations. The atomic data are decomposed into different wavelet levels, and the autocorrelation function at each level is calculated. From the damping of the autocorrelation functions, the vibration lifetime in case of temporal analysis, or the mean free path in case of spatial analysis is evaluated for each level. In comparison with the usual Fourier transformation technique, the technique developed in this research has advantages that (I) the concepts of 'lifetime' and 'mean free path' are clearer, and (ii) mode-dependence of the lifetime or the mean free path is estimated more easily. We have applied this technique to a simple FCC crystal at various temperatures, crystal mixtures, and amorphous systems, and found that the estimated thermal conductivity is in fair agreement with direct estimation of non-equilibrium molecular dynamics simulations. Thus, we conclude that the lattice vibration analysis with the wavelet transformation technique is useful to characterize the thermal properties of solid materials with micro/nano-scale structure.

我们开发了一种新颖的晶格振动分析数值技术，以研究固体振动的寿命和平均自由程，从而研究非金属固体的导热性。该技术利用小波变换来分析通过分子动力学模拟获得的原子位置的时间序列或空间数据。将原子数据分解为不同的小波级别，并计算每个级别的自相关函数。根据自相关函数的阻尼，对每个级别评估时间分析情况下的振动寿命或空间分析情况下的平均自由程。与通常的傅里叶变换技术相比，本研究开发的技术具有以下优点：（i）“寿命”和“平均自由程”的概念更清晰；（ii）更容易估计寿命或平均自由程的模式依赖性。我们已将该技术应用于各种温度、晶体混合物和非晶态系统下的简单 FCC 晶体，并发现估计的热导率与非平衡分子动力学模拟的直接估计相当一致。因此，我们得出结论，小波变换技术的晶格振动分析对于表征具有微/纳米结构的固体材料的热性能是有用的。