臺灣博碩士論文加值系統

摘 要
本文是以分子動力學理論(Molecular dynamics : MD)來研究分子團簇(clusters)碰撞產生之形貌變化、溫度及能量之分析。首先先建構兩分子群所組成的分子團簇，每個分子團簇包含3994顆分子，總數為7988顆。我們給予每個分子團簇不同的相對質心速度去做正向與斜向碰撞，分子間的勢能型式採用Lennard-Jones potential勢能模型來描述，而分子間的作用力則依循牛頓第二運動定律，並使用Gear五階預測修正法來得到分子確實的位置、速度等物理量，並採用統計熱力學理論來求得整個系統之巨觀物理量，如溫度、能量等等。為節省計算時間及減少運算量，運算過程中採用Verlet表列與截斷勢能法(cutoff potential method)。論文中除了討論不同速度下的正向碰撞外，也做了一些斜向碰撞的研究。結果發現在正向碰撞模擬時，當碰撞速度較小時，大部份的動能轉移成振動動能型式而使得兩分子團簇有黏合(coalescence)的現象，相對的如果速度大時，由於能量大，所以發生黏合現象時會有部份的分子產生類似蒸發的現象並脫離原來的分子團簇而濺散(shattering)至四周呈現衛星分佈，使得主分子團中的分子數瞬間減少，溫度上升。另外當速度中等時，兩分子團簇產生反彈分離(reflexive separation)的現象。而當分子做斜向碰撞時，因為分子與分子間接觸部份較小，分子內部束縛力無法克服慣性力，產生拉伸分離(stretching separation)的現象。我們採用的數值模擬法與以往之實驗法不同，特別是針對高速碰撞的散裂情況或是極微小液滴模擬，能補足實驗困難的部分，對於液滴碰撞之現象有很大的助益。

目 錄
中文摘要 ?
英文摘要 ??
誌謝 ???
目錄 ?V
表目錄 V?
圖目錄 V??
符號說明
第一章 緒論 1
1.1 前言 1
1.2 分子動力學理論的文獻回顧 2
1.3 分子碰撞問題的文獻回顧 4
1.4 研究動機與目的 5
1.5 本文架構 6
第二章 物理模型與勢能模式 7
2.1 物理模型 7
2.2 勢能模式之選定 8
2.3 運動方程式 12
第三章 程式計算流程之規劃 16
3.1 分子團簇形成之程序 16
3.2 系統之平衡 18
3.3 分子碰撞流程之規劃 20
3.4 碰撞流程圖及參數的設定 21
3.5 產生之結果 24
第四章 結果與討論 25
4.1 分子團簇之碰撞過程 25
4.1-1 正向碰撞分析 25
4.1-2 斜向碰撞分析 26
4.2 碰撞後分子團簇的溫度與能量之變化 27
4.3 理論分析與實驗結果之比較 28
第五章 總結與未來展望 41
參考文獻 43

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