Dissolution of Alkali Fluoride and Chloride Crystals in Water Studied by Molecular Dynamics Simulations

Abstract

AbstractThe dissolution of cubic crystals of NaF, KF, CsF, LiCl, NaCl, and KCl consisting of 32 cations and 32 anions in an isolated box containing 216 water molecules was studied at 298 K by molecular dynamics simulations. The ion-ion, ion-water and water-water interactions were described in terms of the Tosi-Fumi, Kistenmacher-Popkie-Clementi, and Matsuoka-Clementi-Yoshimine potentials, respectively. During the simulation periods of 12 ps for NaF, CsF and LiCl and 20 ps for KF, NaCl and KCl cations did not dissolve, while anions dissolved from the CsF, LiCl and NaCl crystals but not from the NaF, KF and KCl crystals. The mass effect in the dissolution of CsF was examined by giving the ceasium ions the atomic weight of the fluoride ion (18.998). In case of the "light" caesium ions in the crystal fluctuated less far and again fluoride ions but no caesium ions were dissolved.