Effect of Layer Charge Characteristics on the Distribution Characteristics of HO and Ca in Ca-Montmorillonites Interlayer Space: Molecular Dynamics Simulation.

The charge characteristics of montmorillonite have significant effects on its hydration and application performances. In this study, a molecular dynamics simulation method was used to study the influence of the charge position and charge density of montmorillonite on the distribution of HO and Ca in layers. The results showed that when the layer charge is mainly derived from the substitution among ions in the tetrahedron, a large number of H and O are combined into a hydrogen bond in the interlayer, thus the water molecules are more compactly arranged and the diffusion of water molecules among the layers is reduced. In addition, the Ca are diffused to the sides by a concentrated distribution in the central axis of the layer. As the charge density of the montmorillonite increases, the polarity of the Si-O surface increases, which lesds to the deterioration of the diffusibility of the water molecules and the structure of the water molecules in the interlayers is more stable. The increase in the layer charge density lesds to the expansion of the isomorphic substitution range of the crystal structure, which results in a more dispersed distribution of Ca among the layers under the action of electrostatic attraction between the substituted negative sites and the Ca.