Adsorption, Diffusion, and Dissociation of H₂O on Kaolinite (001): a Density Functional Study

Density functional theory is used to investigate the adsorption, diffusion, and dissociation of H₂O on kaolinite(001) surface. It is found that the preferred adsorption sites on the kaolinite(001) surface for H₂O are the threefold hollow sites with the adsorption energies ranging from 1.06 to 1.15 eV. H₂O does not adsorb on the six−fold hollow site of the aluminium(001) face of the third layer of kaolinite, implying that it is difficult for water molecules to penetrate the ideal kaolinite(001) surface. In addition, we calculate the energetic barriers for the diffusion of H₂O between the most stable and next most stable adsorption sites, which range from 0.073 to 0.129 eV. The results also show that H₂O molecules are easy to diffuse on kaolinite(001) surface. Finally, our study indicates that no dissociation state exists for the H₂O on kaolinite(001) surface.