A microscopic description of concentrated potassium fluoride aqueous solutions by molecular dynamics simulation

We describe the microscopic structure and dynamical properties of potassium fluoride aqueous solutions at T = 298 K as a function of concentration up to 11.9 M. All calculations are made using constant temperature and pressure as well as microcanonical molecular dynamics simulations on the basis of an optimized pair potential model which is a mix of Coulomb plus standard Lennard-Jones short-range terms for water and ion-water interactions and Tosi-Fumi potential for ion-ion interactions. In particular we propose a modified ion-water interaction that successfully reproduces the experimental behavior of the density and water self-diffusion of the solutions as a function of concentration. Finally, we analyze hydrogen-bonding in solutions looking at pair distribution energies and residence times. We find strong evidence for K+-F- pairing in solutions at the higher concentrations.