Analysis of dehydration process in crystallization of NaCl bymolecular dynamics simulations

摘要

Crystal growth in supersaturated NaCl solutions has been investigated by moleculardynamics (MD) simulations. The density profile in the vicinity of interface betweenNaCl(100) and the supersaturated NaCl solution was calculated. Diffusion coefficientsof water molecules in the solution were estimated as a function of distance from thecrystal interface. It is found that the structure and dynamics of the solution at theinterfaces was different from those of bulk solution owing to the effect of electric fieldsdepending on the surface charge. Therefore, the electric field was applied to thesupersaturated solutions and dehydration phenomenon occurring in the process of thecrystal growth was discussed. As the electric field increased, strong hydration structureof Na+ broke out by the electric force. In supersaturated concentration, the solutionstructure is significantly different from that of dilution and has a complicated structurewith hydration ions and clusters of NaCl. If the electric fields applied to the solutions,the breakout of hydration structure was not affected with increasing the supersaturatedratio. This reason is because the cluster structures are destroyed by the electric force.The situation depends on the crystal surface structure by which the electric field occurs.