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

Mobility of water at the (0 0 0 1) 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 approximate to1.25 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. (C) 2003 Elsevier Science B.V. All rights reserved.