Large self-diffusion of water on brucite surface by ab initio potential energy surface and molecular dynamics simulations

Mobility of water at the (0001) surfaces of brucite has been studied using a molecular dynamics method. Ab initio model potential for the water-brucite interaction has been obtained by fitting the parameters to ab initio electronic structure data, calculated by means of the first-principles method based on density functional theory. Using this ab initio model potential, molecular dynamics simulations of a water thin film with the thickness of ≈1.25 nm embedded between the brucite surfaces have been performed at the ambient conditions. Compared with water molecules in the far position from the surfaces, self-diffusion coefficients of water molecules in the vicinity of the surfaces increase by a factor of 1.45 and the reorientation times decrease by a factor of 0.77. This rapid mobility of water on brucite surface results from the weak interaction between water and brucite, and hydroxyl groups of the surface may play a significant role on weakening the water-surface interaction.