Figure 3

Schematic of a representative PNC, and dynamism of the closed system. 3D hcp-like aggregations of Zn²⁺ and OH⁻ ions (without bonding) constitute the PNCs here. Though not drawn for clarity purpose, the Zn²⁺ ions in these PNCs are stabilized by ammonia complexation—as Zn(NH₃)₄²⁺. The extent of PNCs is defined by the temporal solution properties, which keep fluctuating throughout the process. PNCs initially co-exist with non-dense regions. Representative ions/species in the non-dense region is shown around the PNC. The dotted lines represent possible hydrogen bonds between species (This is only qualitative representation, not quantitative). Nucleation starts within the PNCs on expulsion of gaseous molecules, especially ammonia complexed with Zn²⁺ ions that stabilizes these PNCs, and carbonates. The growth follows by the aggregate addition of crystallites formed from these PNCs. Dynamism of gaseous molecules is schematically represented.