以耗散粒子動力學模擬探討水分子的靜電感應作用對相態變化之影響

Effect of Electrostatic Induction on Phase Change of Water Molecule via Dissipative Particle Dynamics Simulation

陳建彣(Jian-Wen Chen)

指導教授 ： 張榮語

國立清華大學/工學院/化學工程學系/碩士(2011年)

摘要

本研究利用耗散粒子動力學(Dissipative Particle Dynamics, DPD)模擬，為了擴大空間與時間的尺度，進而研究在介觀尺度下水分子的靜電感應行為 (Electrostatic Induction Behavior)。過去，關於靜電感應的勢能，在分子動力學上常利用Ewald Summation，因為可以避開在分子間的距離大於截斷半徑時，其靜電勢能會發散的問題。Ewald Summation應用在介觀系統耗散粒子動力學模擬時，在分子間距離為零時，其勢能會發生發散。直到近幾年，這個問題已經被解決。因此，本研究目的分為五部分：
一、 Ewald summation系統的建立以及系統驗證。
二、 從微觀到介觀，Ewald summation修正項的驗證。
三、 建立Ewald summation在耗散粒子動力學模擬系統上。
四、 擴散系統的建立以及系統驗證。
五、 利用耗散粒子動力學，模擬介觀尺度下的水分子，了解其靜電感應行為，並且預測擴散係數。
從最後結果，可以知道隨著部分電荷增加，擴散係數會降低。固定電荷下，隨著Nm加大，擴散係數也會遞減，原因是因為質量影響大過靜電力的影響。

關鍵字

耗散粒子動力學 ； 靜電感應行為 ； Ewald summation ； 水分子

並列摘要

This research, use dissipative particle dynamics simulations,in order to expand the space and time scales,and study the water molecules in the mesoscale electrostatic induction behavior.In past,the electrostatic induction potential regular used Ewald summation,in order to avoid the molecular distance is greater than cut-off radius,the electrostatic potential energy will be divergent problems.Ewald Summation application to mesoscopic systems dissipative particle dynamics simulation,the distance between the molecules is zero,the potential divergence will occur.Until recent years,this problem has been resolved.Therefore,the purpose of this research is divided into five parts: I.Set up the Ewald summation system and verify system. II.From micro to meso,verify Ewald summation correction equation. III.Set up the Ewald summation in the dissipative particle dynamics simulation system. IV.Set up the Diffusion system and verify system. V.Use the dissipative particle dynamics simulation,understand the water molecules in the mesoscale electrostatic induction behavior and prediction the diffusion coefficient. From the result,Know increase the partial charge,the diffusion coefficient will decrease.Fixed charge,the Nm increase,the diffusion coefficient will decrease,because the mass impact is large than static electricity. Key words: Dissipative particle dynamics 、Ewald summation、Electrostatic induction、Water molecules

參考文獻

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