(will be inserted by the editor) Molecular Dynamics Study of Aqueous NaCl Solution: Flush Crystallization Caused by Solution Phase Change

Abstract Solutions at sub- or supercritical conditions receive much attention due to its significance in geology and applications in industrial process. Armellini and Tester showed the experimental results where sodium chloride solution was rapidly mixed with sub- or supercritical water. The morphology difference was observed in the experiment at different pressures. Sodium chloride crystal, which was formed at lower pressure, 200bar, showed porous morphology. In contrast, the crystal formed at higher pressure, 250bar, was amorphous like in shape. The mechanism was ex-plained that the porous crystal came from rapid crystallization without forming vapor-liquid coexistence phase. However, due to short time scale, experimental observation of the underlining mechanism is difficult. Here we conducted micro second time scale molecular dynamics with interfacial system. The correlation be-tween number density of ions and water was proposed to parametrize the solution phase. The correlation and the two dimensional number densities provided us the atomic insight of the flush crystallization, where the vapor-liquid coexistence phase was found at high pressure. Finally, we support the mechanism for the morpholog