本研究是利用分子動力學(Molecular Dynamics)理論模擬奈米銅線在高溫狀態下快速冷卻之晶體型態，並搭配拉伸模擬實驗，探討奈米銅線的結晶度對變形機制、強度、延展性之影響。原子間勢能函數採用嵌入原子式模型(Embedded Atom Method)，並以Verlet鄰近表列法(Verlet List)處理分子與分子間的交互作用。整個數值方法則採用Gear五階預測修正法(Gear’s predictor-corrector algorithms)。
模擬結果顯示，當材料升溫速率愈快獲得非結晶狀態的溫度愈高。而在高溫熔化狀態下快速冷卻後可獲得非均勻的結晶，並發現不同的冷卻速率得到的結晶狀態亦有所改變，冷卻速率愈快，結晶溫度愈低；相反地，冷卻速率愈慢，結晶溫度愈高。在較低冷卻速率的狀態下，可獲得含有缺陷之結晶奈米銅線，而當冷卻速率快到某臨界值時，凝固後可獲得非結晶暫態的奈米銅線，若在室溫下，給予鬆弛一段時間則會恢復成為結晶結構。非結晶奈米銅線在拉伸過程中因臨場結晶效應產生結晶強化現象具有良好的延展性，而冷卻後恢復結晶的奈米銅線因結晶度的不同，塑性變形及破斷機制由缺陷及晶界的性質所決定，故強度及延展性比完美晶體差。

This study analyzes solidification behaviors of copper nanowires under rapid cooling and additionally mechanical properties and deformation behaviors of copper nanowires also investigated with simple tension test after rapid cooling by using molecular dynamics simulation. The Embedded Atom Method (EAM) potential function is employed to describe the atomic interactions. Gear’s predictor-corrector algorithms are adopted to calculate position of each atom.
Analysis results demonstrate that when higher heating rate is applied, the melting temperature of copper nanowires becomes high. It is found that rapid cooling can obtain amorphous nanowires and cooling rate has great effect on the final structure of the copper nanowires during solidification. The higher cooling rate is, the lower crystallization temperature will be and vice versa, the lower cooling rate leads to the higher crystallization temperature. With the decrease of cooling rates, the final structure of copper nanowires varies from amorphous to crystalline. Amorphous copper nanowires have great ductility under tensile loading. Copper nanowires after rapid cooling has lower strength and ductility since plasticity and breaking mechanism determine from defect and behavior of grain boundary in compared to perfect lattice crystal copper nanowires.

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