MODELING THE H3O+-ION - A SIMULATION STUDY OF AN AQUEOUS HCL SOLUTION

A molecular dynamics (MD) simulation study of structural and dynamical properties of a dilute solution of HCI in water is presented. We assume that the acid is completely dissociated at the low concentration which is investigated, and that H3O+ and Cl- are the ionic species. A new model interaction potential is constructed on the basis of available experimental and theoretical information for this cation. In keeping with the flexible model employed for the water, it is also modelled as a flexible entity. The intermolecular H3O+-water potential is constructed on the basis of an ab-initio charge distribution and the short-range parts from the water-water potential. The other potentials are taken from the literature. Simulations of 1.1 m HCl solutions are performed at several temperatures. The structure of the liquid, and specially the hydration of H3O+, are discussed in terms of radial and many-body distribution functions. Dynamical properties are calculated from velocity- and other autocorrelation functions. A stabilization of the pyramidal structure of H3O+ is observed in the solutions.