A molecular dynamics study on the structural and mechanical properties of hydrated kaolinite system under tension

Molecular dynamics method was used to investigate the structural and mechanical properties of hydrated kaolinite with 7, 8.6 and 10 angstrom interlayer spacings. The microstructure parameters of the three systems, such as lattice parameters, volume and d-spacing, were calculated. The diffusion coefficients of interlayer water molecules were calculated and compared with theoretical results. The results for 2D (xy) and 3D motion indicated that the self-diffusion coefficient increased with the increasing of the number of water molecules and kaolinite layers hinder the diffusion of water molecules. Moreover, the dynamics of water molecules confined in kaolinite was analyzed, which demonstrated that strong hydrogen bonds can be formed between water molecules and kaolinite layers, and the hydroxyl surface is hydrophilic. The deformation and failure processes of hydrated kaolinite systems were tracked, and the corresponding stress-strain curves were obtained. In addition, the tensile strength and Young's modulus were derived. The results indicated that the mechanical properties declined significantly with the increasing number of interlayer water molecules, and the [001] direction was the most affected, followed by [010] and [100] directions.