Quantum chemical calculation on clay-water interface

We use a molecular description of the solvent and clay sheet to model the day-water interactions. Quantum chemical calculations both semiempirical (MNDO - modified neglect of differential overlap) and first principle (DFT - density functional theory) were performed on localized cluster models of montmorillonite to study the interaction of one water molecule near the vicinity of the clay surface. The minimized orientation of water molecules with respect to the clay surface is determined. It is observed that lower energy is obtained when the two hydros ens of the water molecule point towards the clay surface i.e. the oxygen of water molecules is going away from the clay surface. The effect of tetrahedral substitution in the clay matrix on the water interaction has also been studied to show that tetrahedral substitution in clays has a distinct effect on the clay-water interaction with respect to stabilization energy. (C) 1997 Elsevier Science B.V.