氯化钾水溶液微观结构的分子动力学模拟研究  

Molecular dynamics simulation of microstructures of potassium chloride aqueous solution

作　　者：王丽娜 张文惠 尚洁莹 赵兴宇 周恒为 WANG Li-Na;ZHANG Wen-Hui;SHANG Jie-Ying;ZHAO Xing-Yu;ZHOU Heng-Wei(Xinjiang Laboratory of Phase Transitions and Microstructures in Condensed Matters,College of Physical Science and Technology,Yili Normal University,Yining 835000,China)

机构地区：[1]伊犁师范大学物理科学与技术学院新疆凝聚态相变与微结构实验室,伊宁835000

出　　处：《原子与分子物理学报》2024年第1期129-136,共8页Journal of Atomic and Molecular Physics

基　　金：新疆维吾尔自治区自然科学基金(2021D01C465);伊犁师范大学博士科研启动基金(2020YSBS009)。

摘　　要：氯化钾水溶液不同于氯化钠的,其在低温下只能形成无水盐和冰.现有研究表明在氯化钠水溶液中不仅存在着水分子连续分布的区域与离子团簇,而且这二者的物质组成也与该溶液所形成晶体的分别对应.为了探寻其他溶液中是否存在此类对应关系,并考察溶液的微观结构,本文采用分子动力学方法对氯化钾水溶液进行了研究,表明了该溶液的一些性质.氯化钾水溶液中K+-K+和Cl--Cl-径向分布函数的特征具有一致性,峰的最大值所对应的位置都分别相同,明显不同于氯化钠水溶液的.系列时刻下瞬态图像内O到其最近离子距离中最大值的统计结果表明氯化钾水溶液中存在着一定大小的水分子连续分布的区域,其平均尺寸至少为2.26 nm;瞬态图像中K+与其最近邻Cl-之间的距离主要分布在0.28 nm~0.38 nm之间,占比约为97.4%;溶液中存在着较大和较小两类离子团簇,较大团簇的平均尺寸为1.73nm,平均离子数是25.0,其内部的离子与周围离子之间具有与氯化钾晶体类似的结构;这些结果表明氯化钾水溶液中也具有微观不均匀性和自聚集效应.将离子间径向分布函数上各峰最大值所对应距离之间的关系与氯化钾晶体中各离子之间距离的几何关系进行对比,并结合离子瞬态图像,给出了离子径向分布函数上各峰的来源,但明显不同于氯化钠水溶液中的情况.另外,通过对比与分析解释了氯化钾水溶液中离子对和团簇形成的原因,并表明原子和离子间相互作用对溶液的微观不均匀具有重要影响.结果还表明氯化钾水溶液中水分子连续分布区域以及离子团簇的物质组成分别与其所形成的冰和氯化钾晶体的组成具有一致性,而且离子团簇的结构和氯化钾晶体的也类似.再结合氯化钠水溶液的结果,表明溶液中存在着与其所能够形成晶体组成类似的对应单元,这为理解溶液中晶体的形成提供了启发.Unlike sodium chloride aqueous solutions(SCAS), potassium chloride aqueous solutions(PCAS) can only form anhydrous salt and ice at low temperatures. Some research results show that not only there are regions with continuous distribution of water molecules(RWs) and ion clusters in the SCAS, but also their composition corresponds to that of the crystals formed from the solution. In order to investigate whether there is such a corresponding relationship in other solutions and research their microstructures, the PCAS is studied by molecular dynamics method and some properties of the solution are gained. The radial distribution functions(RDFs) of K+-K+and Cl--Cl-in the PCAS show that their characteristics are consistent with each other and the positions corresponding to the maximum of their peaks are the same respectively, different from those in the SCAS. The statistical results of the maximum distance between O and its nearest ions in transient images at a series of moments show that there are the RWs with average size of at least 2.26 nm in the PCAS. The distances between K+and its nearest neighbor Cl-in transient images are mainly in the range of 0.28 nm~0.38 nm, accounting for about 97.4%. And the solution has the large ion clusters with average size of 1.73 nm and average ion number of 25.0 as well as small ones, moreover, the structures of their internal ions and surrounding ions are similar with those of potassium chloride crystals. These results show that micro heterogeneity and self-concentration effects also exist in the PCAS. The origins of each peak on the RDFs of ions are shown by comparing the relationships between distances of the maximum value of the peaks with the geometric ones of distances between ions in potassium chloride crystal and analyzing the ion transient images, and they are different from the SCAS. In addition, why the ion pairs and clusters are formed in the PCAS is explained by corresponding comparison and analysis;meanwhile, it is shown that the micro interaction of atoms and ions has

关 键 词：氯化钾水溶液 离子团簇 分子动力学 结晶 

分 类 号：O645[理学—物理化学]