Refinements of water parameters for molecular dynamics: Simulations of adsorption at the clay mineral/aqueous solution interface

In the context of a long-term program involving molecular dynamics simulations of adsorption phenomena at the clay mineral/aqueous solution interface, we are testing the viability of combining a force field that we developed specificially for clays with other, independently derived potential parameters for molecular species which are important in clay adsorption.

For the current study the importance of variations in the potential parameters of water were investigated and polarization effects on oxygen studied as a function of intermolecular interactions. For this purpose ab initio MP2/6-311GG atomic charges were determined for several oligomers of water and for the water dimer at different intermolecular separations.

Charge variations of up to ~0.1 electron charge unit on oxygen are found and, together with changes in van der Waals constants, their significance for dynamics simulations of hydrated clays is described.