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运用分子动力学(moleculardynamics,MD)方法分别研究了含有32,64和96个水分子的Li-,Na-,K-蒙脱石层间阳离子与水分子的位置和结构.计算结果表明蒙脱石层间阳离子位置与四面体和八面体电荷位置及离子的大小有关.一层水合物中可以观察到三种阳离子都能和四面体电荷与八面体电荷位置分别形成内、外配位作用.二层水合物中,仍然可以观察到Li+和Na+与电荷位置的配位作用,但是已经开始向层中其他方向扩散,而K+仍然在粘土的表面附近.三层水合物中,Li+,Na+开始从电荷位置和表面分离,K+也开始向层间其他方向扩散.水分子在所有三种水合物中都分散于层间各个方向.径向分布函数的分析结果表明层间三种阳离子组织水分子的能力不同,水化作用随着阳离子半径的增大而减弱;此外层中水分子的聚合程度随着水分子的增加而加强,水分子的结构也不同于模拟的液体水分子的结构;说明蒙脱石层间阳离子的溶剂化作用对水分子的组织起着重要的作用.
The positions and structures of interlayer cations and water molecules of Li-, Na- and K-montmorillonite containing 32, 64 and 96 water molecules were studied by using molecular dynamics (MD) method. The calculated results show that montmorillonite The position of the cation between the layers is related to the charge position of the tetrahedron and the octahedron and the size of the ions, and it can be observed in the layer of hydrate that both the cations and the tetrahedral charge and the octahedral charge position form the internal and external coordination functions, respectively. In the two-layer hydrate, the coordination of Li + and Na + with the charge sites is still observed, but it has begun to diffuse in other directions in the layer and K + remains near the surface of the clay. In the three-layer hydrate, Li + and Na + begin From the charge location and surface separation, K + also began to diffuse in other directions of the interlayer.The water molecules were dispersed in all three layers in all three hydrates.The analysis of radial distribution function showed that the three cationic water molecules The hydration decreases with the increase of cation radius; the degree of polymerization of water molecules in the outer layer increases with the increase of water molecules, and the structure of water molecules is also different from that of simulated liquid water molecules Structure; explain the solvation of the interlayer between the montmorillonite plays an important role in the organization of water molecules.