摘要
在 L i Br与水的物质量比分别为 1∶ 64、1∶ 32、1∶ 16、1∶ 8、1∶ 4和 1∶ 3的情况下 ,对 L i Br溶液从低温到高温的分子动力学模拟进行了研究。随浓度增加 ,锂离子的水合数量呈减少趋势但同时又从 L i+- Br-接触离子对的数量增加中得到补偿 ,而 L i离子的第一配位壳层的配位数量保持不变。在高浓度 Li Br溶液中 ,Br- O之间的距离有所增加 ,Br-- O的径向分布的形状更趋于非对称 ,从而很好地确定了 Br离子水合壳层 L i+- Br-接触离子对可以在更稀的溶液中产生 ,但随浓度增加而增加。L i+- Br-距离明显短于溶液中 Li离子与 Br离子的离子半径之和 ,也短于 L i Br晶体中两者离子半径之和。高浓度溶液中水分子的结构几乎被破坏 ,水分子间的氢键明显增加 ,但没有消失。对 L i+。
Molecular dynamic simulations of aqueous LiBr solutions from low concentration to high concentration with the molar ratio of LiBr: H 2O of 1∶64,1∶32,1∶16,1∶8,1∶4,and 1∶3were carried out. The hydration number of Li ion decreases with increasing concentration, but this is compensated by the increasing number of Li + Br - contact ion pairs, and the coordination number of the first coordination shell of Li ion keeps approximately unchanged. The hydration shell of Br ion is well defined in highly concentrated LiBr solutions with the Br - O distance a little expanding and the shape of radial distribution function of Br - O more asymmetric. The contact ion pairs of Li + Br - appear even in more dilute solutions, and increase with the increasing of concentration. The Li + Br - distance is obviously shorter than the sum of ionic radii of Li ion and Br ion in aqueous solution, also shorter than that in LiBr crystals. The structure of water molecules in highly concentrated solutions is nearly destroyed, and the hydrogen bond among water molecules decreases markedly, but does not disappear. The calculated diffusion coefficients of Li +,Br -,and H 2O are comparable to the experimental values.
出处
《盐湖研究》
CSCD
2000年第4期8-18,共11页
Journal of Salt Lake Research
基金
国家自然科学基金资助项目(29771032)
关键词
分子动力学模拟
溴化锂溶液
配位数
离子对
Molecular dynamic simulation
Aqueous LiBr solution
Radial distribution function
Coordination number
Ion pair
