Crystallization

What is crystallization? It is the process of formation of solid crystals precipitating from a solution, melt or most rarely deposited directly from a gas. The process of crystallization consists of nucleation and crystal growth.

Nucleation is the process where solute molecules dispersed in the solvent start to gather in clusters. However, for nucleation to take place, the clusters must be stable, or they would redissolve. Therefore, the solution must be saturated in order for crystallization to take place. The stable clusters constitutes to the nuclei. The nuclei would then cause more precipitation to occur. The process of nucleation is also when the atoms would move to form an atomic structure of a crystal.

Then, crystal growth is the subsequent growth of the nuclei that succeed in achieving the critical cluster size. As this is happening, nucleation continues to take place. This two processes can continue to take place in the presence of existing supersaturation. Depending on the conditions, either nucleation would predominant over growth or the other way round. This results in the different shapes and sizes of crystals.