Atomistic nature of NaCl nucleation at the solid-liquid interface.

Area of Science:

• Physical Chemistry
• Materials Science
• Chemical Engineering

Background:

• Heterogeneous nucleation is crucial for crystallization processes.
• Understanding NaCl nucleation at interfaces informs industrial crystallization.
• The role of water in ion deposition is not fully understood.

Purpose of the Study:

• To investigate the early stages of NaCl heterogeneous nucleation.
• To determine the critical nucleus size at the water-NaCl (001) interface.
• To elucidate the influence of water and interfacial forces on nucleation.

Main Methods:

• Molecular dynamics simulations were employed.
• Simulations focused on supersaturated NaCl aqueous solutions.
• The water-NaCl (001) interface was studied.

Main Results:

• The critical nucleus size was found to be as small as a two-atom (Na(+)-Cl(-)) ion pair at high supersaturation.
• Stable nuclei contained more Na(+) than Cl(-) ions due to water network and hydration forces.
• Differential deposition of ions created a positively charged substrate, acting as an additional nucleation driver.

Conclusions:

• Water plays a significant role in NaCl nucleation, influencing ion deposition and substrate charge.
• Interfacial water networks and hydration forces are key factors in early-stage nucleation.
• The findings suggest a multi-faceted driving force for nucleation beyond simple supersaturation.