ABSTRACT
The early stage of crystallization is the formation of three-dimensional (3D) nu clei in the mother phase (vapor, solution, melt); the second step is represented by the advancement of the faces bounding these nuclei. Nucleation and growth are not equilibrium processes: crystal nucleation can occur within a supersatu rated bulk phase without the intervention of foreign particles or substrates (homo geneous nucleation), but this event is not easily found in natural and in laboratory environments where preexisting solid surfaces can promote the formation of a new crystal phase (heterogeneous nucleation). According to Boistelle [1], we define, as a first step, the equilibrium and supersaturation conditions of a mother phase in contact with its own crystals; later we confine our attention to the factors determining the advancement rate R of the crystal faces under fixed values of the crystallization temperature (Tc) and the supersaturation (Δμ). These factors can be roughly divided into two categories.
