臺灣博碩士論文加值系統

本研究以分子動力學理論為基礎並結合高效能和MPI平行化的程式設計，模擬水分子在介觀級奈米尺度下相關的物質特性和現象並進一步提出物理解釋與探討。
在液態與超臨界狀態下均質系統中水分子性質的模擬，利用徑向結構分佈函數探討的氣液相態結構分佈和特徵，發現分子間形成氫鍵的距離約1.86埃；擴散係數隨溫度升高和壓力下降而上升，超臨界的擴散能力優於常溫液態；液態下形成氫鍵配位數為三或四的比例居多，兩者加總大約佔整體的59%∼86%以上，分子間氫鍵效應較為明顯。在微液膜蒸發過程的模擬，發現於液膜表面存在一連續密度變化的過渡層，並且計算出介面厚度隨溫度上升而增加；結合Shrage的理論模式，計算微液膜的蒸發係數，數值範圍約0.3∼0.6之間且隨介面壓力增加而呈現增加的趨勢；利用PV-WIN影像處理，可具體觀察分子在介面凝結蒸發和真空中動態過程和碰撞機制。奈米液滴在恆溫白金表面的模擬，液滴經歷不同的物理階段：初期表面吸附、擴散形成薄膜、等溫加熱蒸發和乾化、於真空中叢聚成核以及合併重新凝結成液滴，並伴隨不同的能量變化；根據接觸角的計算，顯示液滴吸附於白金表面過程屬於親水效應。

The present study simulates some material properties and phenomena of water in the minute nano scale by molecular dynamics simulation theory and high performance programming with MPI parallel method. We also further discuss those simulation results and offer some arguments with appropriate point of physical view.
In a homogenous system, water molecules are simulated at two different thermodynamic states including liquid at various different temperature and supercritical water. According to radial distribution functions, a distance of hydrogen bond between two water molecules is about 1.86 angstrom. Self-diffusion coefficient increases with the temperature and decreases with pressure. Capability to diffuse at supercritical states is better than at liquid states. Moreover in a liquid water state, there are much higher percentage with three or four the average number of hydrogen bonds formed by each molecule and stronger hydrogen interaction than that in a supercritical state. Summing percentage of two parts is about between 59% and 86%.
Simulating evaporation processes of a thin liquid water film demonstrates that there is a transition layer with density varying continuously on a thin liquid film and this interfacial thickness increases with increasing temperature. Based on the Schrage model, the evaporation coefficients of thin liquid film are between 0.3 from 0.6 and increase with interfacial pressure. It is very evident to observe that molecules take place processes of evaporation and condensation at the interface of liquid film and collisions in a vacuum by using image software celled PV-WIN.
There are various different physical processes when a nano-water droplet is close to an isothermal platinum surface: contact, adsorption, surface diffusion, evaporation and platinum surface to dry off, nucleation of cluster and reformation of droplet. Besides, total energy of droplets changes during different states. Finally, according to measuring contact angle, the platinum surface is found to be hydrophilic to the nano-water droplet.

摘要 I
Abstract II
致謝 IV
目錄 V
圖目錄 IX
表目錄 XV
第一章 緒論 1
1-1 研究背景與動機 1
1-2 研究方法與目的 3
1-3 論文的架構 5
第二章 文獻回顧 7
2-1 分子動力學之相關文獻 7
2-2 均質水分子模擬之相關文獻 8
2-3 微液膜蒸發之相關文獻 11
2-4 微流體在金屬表面上模擬之相關文獻 13
第三章 分子動力學理論 15
3-1 核心理論 15
3-2 分子位能勢函數 15
3-2.1 氬原子間的位能勢函數 16
3-2.2 水分子間的位能勢函數 17
3-2.3 水分子與白金原子間的位能勢函數 19
3-3 週期性邊界條件 20
3-4 最小映射法則 21
3-5 分子間作用力計算的簡化 21
3-5.1 牛頓第三運動定律 22
3-5.2 截斷半徑 23
3-5.3 Verlet相鄰列表 24
3-6 計算精確度的提升 26
3-6.1 常用數值積分方法 26
3-6.2 計算參數無因次化 27
3-7 計算程式平行化 27
3-7.1 MPI平行程式設計 28
3-7.2 應用於分子動力學計算 29
3-7.3 平行電腦簡介 33
3-8 初始條件的設定 34
3-9 系統的溫度控制與程式的主體架構 35
第四章 均質系統的水分子模擬 45
4-1 水分子的基本結構 45
4-2 模擬系統參數的設定 46
4-3 徑向結構分佈函數 48
4-4 自我擴散係數 50
4-5 水分子的氫鍵配位數 52
第五章 微液膜的蒸發模擬 67
5-1 前言 67
5-2 模擬系統的相關設定 68
5-3 微液膜的密度分佈 69
5-4 氣液介面厚度相關分析 70
5-5 微液膜的溫度分佈 71
5-6 微液膜蒸發係數計算 72
5-7 微液膜的分子蒸發機制 74
第六章 奈米液滴在恆溫白金面的物理現象模擬 100
6-1 前言 100
6-2 白金基版的溫控模式 101
6-3 模擬系統的相關設定 102
6-4 各個階段的物理現象 103
6-5 各個階段的能量變化 108
第七章 結論與建議 127
參考文獻 131

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