本研究主要以非平衡態分子動力學模擬方法探討T型奈米碳管的熱干涉效應，在T型碳管的兩分支末端分別放置冷熱區，藉由改變自由分支長度觀察冷熱端的熱流變化趨勢，考慮聲子波動性，將接頭處視為分光鏡將聲子分流、自由分支長度造成聲子路徑差，從聲子波動干涉的角度來探討其熱流變化。本論文首先介紹分子動力學的基礎理論和非平衡態分子動力學模擬方法的原理，然後介紹干涉的物理意義。在建立原子模型時，透過熱焊方式合成出不同缺陷型態的T型接頭，本研究將分別探討接頭之原子組態、控溫分支冷熱層位置、分支碳管長度和系統溫度，對冷熱端熱流的影響。
本研究的模擬結果發現，即使在不同的系統溫度下(50K、300K、600K)，自由分支長度對系統熱流影響非常小，並未觀察到聲子波動干涉效應，且低溫下的熱流值最高，在高溫時，熱流值震盪較明顯，應該是高溫熱擾動所造成；改變控溫分支的位置及不同接頭之原子組態下，熱流變化皆有相似的趨勢，但皆未觀察到熱干涉效應。最後以聲子態密度分析熱流在不同自由分支長度下的變化，進行討論，推論改變碳管自由分支長度對熱流影響不顯著，一個可能性為T型接頭上的缺陷破壞了聲子波動性，造成聲子散射；另一個可能性為熱流由不同波長之聲子所貢獻，改變路徑下，不同聲子相位差的能量總和相似，所以造成熱流變化不大。

In this study, we used non-equilibrium molecular dynamics(NEMD) simulation to investigate the thermal interference effect in branched carbon nanotube(CNT) with T-junction. The cold and hot regions were placed at the end of two branches and the free branch length effect on the heat current were simulated. First, the atomic model of the T-junction was created by thermal welding at high temperature and T-junction models with different topological defects were constructed in order to study the junction atomic configuration effect. We also explored the temperature effect and the position of the temperature controlled region effect on heat current inside branched CNT.
From our simulation, it was found that the free branch length of T-junction CNT did not affect the heat current noticeably, irrespective to the system temperature. At low temperature, i.e., 50K, the heat current value was higher as compared to those in higher temperatures. The heat current fluctuation was larger at high temperature, i.e., 600K, due to thermal perturbation. As for the junction atomic configuration as well as the position of temperature-controlled regions, we observed similar heat current dependence on free branch length. Overall, there was no thermal interference phenomena observed in our simulation. We attempted to perform analysis using phonon density of states (PDOS) on the branches to provide explanation for the heat current in the branched CNT. There were two possible postulations. One was that the topological defects at the junction destroyed the wave properties of phonons and most phonon transport became diffusive, instead of ballistic. The other was that the heat current was the total contribution of many phonons with various wavelengths. The summation of all the thermal energy carried by phonons with different phase differences would not show obvious dependence on the branch length.

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