摘要:
通过构建晶体表面-KDP分子界面吸附结构模型,采用分子动力学和密度泛函计算方法研究KDP分子在（001）和（010）面吸附的物理化学过程,考察了温度对物理吸附行为的影响.研究表明：KDP晶体表面的吸附过程和生长习性主要由化学吸附主导,化学吸附能的计算表明[K-O_8]基元在（001）界面的结合能是（010）界面结合能的2.86倍;在饱和温度附近,[H_2PO_4]ˉ阴离子在KDP界面的物理结合能随温度的变化呈现振荡特征,溶液中有较多的离子团簇形成,溶液变得很不稳定;当温度从323 K降低至308 K时,水分子在界面的结合能总体呈下降趋势,而KDP分子在界面的吸附能总体呈上升趋势,脱水过程是水分子和[H_2PO_4]ˉ阴离子在固液界面边界层竞争吸附的结果.研究结果对确足晶体生长界面动力学过程发展和完善晶体生长理论有重要意义.
Abstract:
Through building ＂surface-molecule＂ interfacial adsorption structure model,the physical and the chemical absorptions of（001） interface and（010） interface of KDP crystal are studied by using molecular dynamics and density functional theory method,and the effect of temperature on physical absorption behavior is investigated.The result indicates that the absorption process and the growth habit of KDP surface are dominated by the chemical absorption,and the binding energy on（001） surface is 2.86 times that on（010） surface of KDP crystal.Near the saturation temperature,the binding energy between[H_2PO_4]~- anion and crystal surface presents obviously an oscillation characteristic with the temperature varying,and the solution becomes unstable with the formation of anion clusters.With temperature decreasing from 323 K to 308 K,the binding energy of H_2O decreases in general,but the binding energy of KDP molecular increases obviously,which indicates the dehydration process results from the competitive absorption between H_2O and[H_2PO_4]~-.The results obtained are of significance in identifying the surface kinetics process and developing more sophisticated crystal growth theories.
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