Chaitanya Jitendra Shah

Mechanism of Crystal Nucleation of NaCl from Aqueous Solution

Compared to crystal nucleation from a melt, simulating crystal nucleation from a solution is very challenging. Crystal nucleation from solutions is dominated by slow diffusion of solute molecules from the bulk to the crystal-solution interface which makes the nucleation process very slow and thus difficult to investigate in MD simulations. Another technical challenge in simulating crystal nucleation is the need to maintain the supersaturation in the bulk of the solution during crystal growth. Toward overcoming these challenges, our group had developed a molecular theory of nucleation from dilute phases [1]. In addition, the molecular theory can predict the free energy landscape for a range of supersaturations without the need for additional simulations at every supersaturation. In this work, we apply the molecular theory to one of the well-studied systems, i.e., crystal nucleation of NaCl from an aqueous solution. Our calculations reveal that the topology of the free energy landscape of the NaCl nucleus in solution is shaped by a complex interplay of aggregation, crystallinity and dehydration. We are also able to obtain detailed insights into the molecular mechanism of NaCl crystal nucleation, which were lacking in earlier studies.

Ref: 1. R. Addula, S. Punnathanam, Phys. Rev. Lett., 126, 146001 (2021)