高浓度氯化钠水溶液的微观结构与析出晶体之间关系的研究

doi:10.16553/j.cnki.issn1000-985x.2024.0198

摘要/Abstract

摘要： 为了探究无机电解质水溶液的微观结构与析出晶体之间的关系,本文对高浓度氯化钠水溶液进行了分子动力学模拟研究,并结合低浓度氯化钠水溶液及氯化钾水溶液的结果进行了讨论。离子团簇的分析结果表明电解质水溶液析出的晶体在组成和几何关系上都与溶液中的离子团簇是对应的,说明溶液能够析出的晶体的组成方式和几何结构已经存在于母相溶液之中,析出的晶体与溶液的微观结构具有对应关系。径向分布函数、离子间距和瞬态图像的结果显示,高浓度氯化钠水溶液中只存在着直接接触离子对和部分间隔离子对,分别对应于Na⁺-Cl^-径向分布函数上的第一峰和第二峰。与低浓度氯化钠水溶液相比,直接接触离子对的比例显著提高,而部分间隔离子对的比例则大幅下降,完全间隔离子对消失,表明溶液中离子间的结合方式会随浓度发生转变;离子间结合方式的变化是导致溶液微观结构及所析出晶体结构变化的原因。溶液中水分子构成的纯水团簇和Na⁺与Cl^-构成的离子团簇的存在,说明高浓度的氯化钠水溶液中具有自聚集效应。本文的结果将为溶液析晶与结晶过程的理解及溶液微观结构的认知提供启发。

关键词: 溶液析晶; 氯化钠水溶液; 离子团簇; 微观结构; 分子动力学模拟

Abstract: In order to investigate the relationship between microstructures of inorganic electrolyte aqueous solutions and crystals formed from them, the high concentration sodium chloride aqueous solutions were researched by molecular dynamics simulation based on Lammps software and the results are discussed in combination with those of low concentration sodium chloride aqueous solutions and potassium chloride aqueous solutions. The water molecules are modelled by the SPC/E model and the interactions between particles is described by Coulomb interactions and Lennard Jones potentials. The mass fraction of sodium chloride is 28.21% in the solution, pressure and temperature are 1 atm (1 atm=101.325 kPa) and 380 K, respectively. The analysis results of ion clusters show that the composition and the geometric relationship of the crystals formed from the electrolyte aqueous solution correspond to those of the ion clusters in the solution, indicating that the composition and the geometric structure of the crystals formed from the solution already exist in the parent phase solution and that the crystals have a corresponding relationship with the microstructure of the solution. The results of the radial distribution functions, distances between ions and snapshots show that only directly-contacting ion-pairs and partially-spaced ion-pairs exist in the high-concentration sodium chloride aqueous solution, corresponding to the first and second peaks of Na⁺-Cl^- radial distribution functions in turn. Compared with the results of the low-concentration sodium chloride aqueous solution, the proportion of directly-contacting ion-pairs and that of partially-spaced ion-pairs respectively increases and decreases significantly while completely-spaced ion-pairs disappear, indicating that the pairing mode of ions would change with solution concentration; the transformation of the pairing mode of ions is the reason for the variation of the microstructure of solutions and for that of the structure of the crystals formed from solutions. The existence of pure water clusters composed of water molecules and ion clusters composed of Na⁺ and Cl^- in the solution states that the self-concentration effect is presented in the high-concentration sodium chloride aqueous solution. The results in this paper could provide an insight into the understanding crystallization and microscopic structure of solutions.

Key words: crystallization of solution; sodium chloride aqueous solution; ion cluster; microscopic structure; molecular dynamics simulation

中图分类号:

O645.1

白世玉, 赵兴宇, 林佳玮, 权国强, 王丽娜. 高浓度氯化钠水溶液的微观结构与析出晶体之间关系的研究[J]. 人工晶体学报, 2025, 54(4): 700-707.

BAI Shiyu, ZHAO Xingyu, LIN Jiawei, QUAN Guoqiang, WANG Lina. Relationship Between Microstructures of High Concentration Sodium Chloride Aqueous Solutions and Crystals Formed from Them[J]. Journal of Synthetic Crystals, 2025, 54(4): 700-707.

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