以分子動力學探討鹽類離子與水團簇的結構與鍵結行為

Studies on the Behavior and Structure of Water Cluster and Ion System by Molecular dynamics simulation

王偉儒(Wei-Ju Wang)

指導教授 ： 張榮語

國立清華大學/工學院/化學工程學系/碩士(2010年)

摘要

以往分子動力模擬對於有帶電粒子系統較不易處理，主要是因為靜電力的收斂緩慢，若強制使用截斷半徑則會對力的計算上產生相當大的誤差。所幸藉由Ewald sum來處理靜電力，可得到合理的計算結果。但是Ewald sum方程式複雜，因此須先得到正確的作用力處理式才能夠運用於分子動力模擬中。

本研究可分為三個部份：
I.首先推導出Ewald sum以得到正確的計算式，接著驗證Ewald sum程式
化過程無誤。
II.將成功得到的計算式運用於分子動力模擬-建立純水系統。
III.最後建立鹽類水溶液。

研究最後探討各種離子對與不同的濃度對於水分子間氫鍵的影響，結果發現離子對於水分子間氫鍵的破壞與離子的水合能力是成正比關係。

關鍵字

Ewald sum ； 離子水合 ； 分子動力模擬

並列摘要

Because of the slow convergence of static electricity, a molecular dynamic simulated system for charged particles is difficult to handle. If we force to use the truncation radius, the calculation of forces will generate considerable errors. However, by using Ewald sum which deals with static electricity, we are entitled to get reasonable results. But, Ewald sum formula is too complex to use. The force should be gotten first, so the correct address type can be applied in molecular dynamic simulation.

The research can be divided into three parts:

I. Get the right formula by derived Ewald sum, then verify if the Ewald sum
program process is correct or not.

II. Apply the formula into molecular dynamics simulation - the established water
system.

III. Establish salt solution.

Finally, the research is discussing about the effect of hydrogen bonds between water molecules and ions in different concentrations. The result shows that the destruction of hydrogen bonds between water molecules and ions is proportional to hydration.

並列關鍵字

Ewald sum ； ion hydration ； molecular dynamics simulation

參考文獻

1. Callister, W.D., materials science and engineering: an introduction. 2006: John Wiley & Sons,Inc.

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3. Alder, B.J. and T.E. Wainwright, Studies in Molecular Dynamics. I. General Method. J. Chem. Phys., 1959. 31: p. 459-466.

4. Alder, B.J. and T.E. Wainwright, Phase Transition for a Hard Sphere System. J. Chem. Phys., 1957. 27: p. 1208-1209.

5. A.Rahman, Correlations in the Motion of Atoms in Liquid Argon. Phys.Rev, 1964. 136: p. A401-A405.