KDP晶体水溶液微结构和界面吸附行为研究

Molecular Dynamics Study on Microstructure of KDP Cystal Solution and Interface Adsorption Behavior

本文采用分子动力学模拟方法研究了磷酸二氢钾(KDP)晶体水溶液的微观分子结构以及生长基元的界面吸附行为。在分子动力学模拟中,水分子采用简单点电荷(三节点)模型,钾阳离子为带电硬球模型,磷酸二氢根离子采用七节点模型,计算了KDP水溶液的构型能,对比分析了(010)和(001)两个晶面的生长速率。研究结果发现:在饱和温度附近体系的局域粒子数密度有剧烈涨落,过饱和溶液的比热显著高于不饱和溶液的比热,表明在饱和温度以下KDP溶液经历了结晶相变过程;磷酸二氢根阴离子生长基元在(010)和(001)两个晶面生长行为的研究表明(010)面生长速率明显高于(001)面,得到了与实验和从头计算相符的结果。

The internal energy and microstructure of potassium dihydrogen phosphate （KDP） solution at different temperature and the interface adsorption behavior were studied by molecular dynamics simulation. The water molecule was treated as a simple-point-charge （SPC） model, and a seven-site model for the dihydrogen phosphate ion was adopted. The internal energy function and the radial distribution function （RDF） of the solution were studied in detail. An unusually large local particle number density fluctuation was observed in the system at saturation temperature. It was found that the specific heat of oversaturated solution is higher than that of unsaturated solution, which indicates the solution experience a crystallization process below saturation temperature. By comparatively studying the adsorption behavior on the surface of （010） and （001） we find that the growth rate of （010） surface is much higher than （001） surface.