MD simulation of crystal growth of NaCl from its supersaturated aqueous solution

Crystal growth from a supersaturated NaCl aqueous solution has been studied by molecular dynamics (MD) simulation. The model was similar to the one previously applied by us for a NaCl melt. 168Na+, 168Cl− and 192H2O were set up in a basic cell in the following way: four layers of a NaCl seed crystal were disposed with the (100) plane of 32(Na++Cl−) in contact with a supersaturated NaCl aqueous solution consisting of 40(Na++Cl−) and 192H2O. The solution was first equilibrated in contact with the 'frozen' crystal. Two-dimensional periodical conditions were imposed in the directions along the interface. In the direction normal to the interface, the aqueous solution is directly open to vacuum. Only one combination of pair potentials among the five different combinations of inter atomic potentials studied led to crystallization of NaCl. Thus, it strongly depends on the pair potentials used whether a crystal grows from its aqueous solution. After the equilibration run, a run longer than 2 ns was performed. Crystals gradually grew as clusters in the solution, but not uniformly on the seed crystal, which is in contrast to the growth from a NaCl melt.