Akhiezer机制在室温非晶中的弛豫
Akhiezer Mechanism Dominates Relaxation of Propagons in Amorphous at Room Temperature
摘要：
电子在调节纳米结构非晶材料的热导率方面起着重要的作用。虽然在用分子动力学定量评估传播子弛豫时间方面取得了进展，但其弛豫机制仍有待探索。在这里，我们调查的传播在非晶硅，非晶二氧化硅，和非晶氮化硅在室温下的Akhiezer模型，其中的参数进行晶格动力学和分子动力学分析评估的弛豫过程。结果表明，Akhiezer模型能很好地再现各种测量方法得到的实验结果，表明Akhiezer机制在室温下传播子的弛豫过程中起主导作用.此外，我们表明，适当的传播声速是德拜声速的80%左右，相当于横向模式的声速。我们还发现，这些非晶的总热导率的扩散子的贡献是相似的，这是1 W/m K左右，而传播子的贡献显着不同的材料，这是30%的非晶硅和二氧化硅，但可以高达70%的非晶氮化硅。
英文摘要：
Propagons play an important role in tuning the thermal conductivity of nanostructured amorphous materials. Although advances have been made to quantitatively evaluate the relaxation time of propagons with molecular dynamics, the underlying relaxation mechanism remains unexplored. Here, we investigate the relaxation process of propagons in amorphous silicon, amorphous silica, and amorphous silicon nitride at room temperature in terms of Akhiezer model, the parameters of which were evaluated by performing lattice dynamics and molecular dynamics analysis. The results show that the Akhiezer model can well reproduce experimental results obtained by various kinds of measurement methods, indicating that Akhiezer mechanism dominates the relaxation process of propagons at room temperature. Moreover, we show that the appropriate sound speed of propagons is around 80% of the Debye sound speed and comparable to that of the sound speed of the transversal modes. We also reveal that the contribution of diffusons to the total thermal conductivity of these amorphous is similar, which is around 1 W/m K, while the contribution of propagons varies significantly depending on the materials, which is 30% in amorphous silicon and silica but can be as high as 70% in amorphous silicon nitride.
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