电解质溶液界面结构的分子动力学模拟研究

电解质溶液界面结构的研究不仅具有重要的理论意义, 而且具有一定的实用价值. 采用分子动力学模拟研究了LiCl, LiBr, LiI, NaI, KI, CsI水溶液中阴阳离子在1×105 Pa和300 K下的气液界面分布情况, 探讨离子水化与电解质溶液界面结构的关系, 并分析阳离子水化能力的强弱对共存阴离子在界面富集分布的影响. 通过对模拟结果的分析发现, 离子的水化能力越强, 就越能形成稳定的水化结构而处于本体相中, 水化能力越弱, 则越易在界面富集. 该机理合理地解释了离子在界面的分布现象, 阳离子水化能力一般较其共存阴离子强而处于本体相, 阴离子则趋向在界面处富集; 不同阴离子在界面的密度分布也与阴离子的水化能力相关, 阴离子水化能力越弱, 其在界面富集程度越高, 不同阴离子在界面的富集趋势为Cl－＜Br－＜I－; 阳离子水化能力的强弱也影响其共存阴离子在界面的富集程度, 阳离子的水化能力越弱, 其共存阴离子在界面的富集程度就越低.

Molecular Dynamics Simulations on the Interfacial Structures of Electrolyte Solutions

Studies on interfacial structures of electrolyte solutions are not only of theoretical significance, but also valuable for practical applications. In this work, molecular dynamics simulations were carded out to investigate the interfacial properties of LiCl, LiBr, LiI, NaI, KI, CsI solutions at 1× 10~5 Pa and 300 K. which was aimed to discover the relationship between hydration theory and interracial structures of electrolyte so-lutions. The effect of hydration strength of cations on interfacial structures of anions was explored. Simula-tion results indicate that for those with stronger hydration ability, they tend to stay in the bulk region whereas for ions with weaker hydration ability, they tend to aggregate in the interfacial region. This mechanism pro-vides a reasonable explanation for the distribution behavior of ions at interfaces. The hydration ability of cations is usually stronger than that of anions, so cations tend to stay in the bulk region while counter anions prefer to aggregate in the interfacial region. The interracial profiles of anions are closely related with their hydration ability, the weaker the hydration ability, the higher the interfacial profiles at interfaces. The ten-dency of anion aggregation at interfaces is Cl~-