  In this study, molecular dynamic simulations are employed to investigate the
nucleation of NaCl crystal in solutions. According to the simulations, the
dissolved behaviors of NaCl in water are dependent on ion concentrations. With
increasing NaCl concentrations, the dissolved Na$^+$ and Cl$^-$ ions tend to be
aggregated in solutions. In combination with our recent studies, the aggregate
of dissolved solutes is mainly ascribed to the hydrophobic interactions.
Thermodynamically, no barrier is needed to overcome in the formation of the
solute aggregate. This is different from the two-step nucleation mechanism. In
comparison with the classical nucleation theory (CNT), due to the aggregate of
dissolved solutes, this lowers the barrier height of nucleation, and affects
the nucleation mechanism of NaCl crystal in water.
