Heterogeneous Nucleation

Heterogeneous nucleation occurs when a new phase, like a crystal or droplet, forms on a surface or impurity within a material, rather than in the bulk. This surface provides a favorable site that lowers the energy barrier needed for the new phase to grow. For example, ice forms more easily on a cold window than in the open air because the glass surface helps the ice crystals start forming. This process is common in nature and industry, influencing everything from cloud formation to the design of materials and coatings.