Investigating Dissolved Carbon Dioxide Diffusion between Saturated Kaolinite-Slit Confinement using Molecular Dynamics Simulations.

A series of equilibrium and nonequilibrium molecular dynamics simulations were conducted to investigate the Fickian diffusion of dissolved carbon dioxide under kaolinite-slit confinement. The relationship between the chemical potential of the dissolved carbon dioxide and its molar fraction was revealed. The Fickian diffusion coefficients were also computed and were found to increase linearly with the molar fraction. The adsorption behavior of the dissolved carbon dioxide as a solute was found to be associated with the accumulation and preferential orientation of the solvent water. The radial distribution functions of the water oxygen in various regions were analyzed, revealing the spatial inhomogeneity of the solvent structure. The inhomogeneity of dissipation, quantified by local mobility, was found to be proportional to the first peak of the radial distribution function of solvent water.