Factors Controlling the Morphology of Crystals

Factors controlling the morphology of crystals are analysed based on the concept of solid-liquid interface roughness. Mutual relations among dendritic, hopper and polyhedral morphologies of crystals are explained on the basis of growth rate vs. supersaturation relations. There are two transitional supersaturations σ*and σ**. Above σ** dendritic morphology is expected, whereas below σ* polyhedral crystals bounded by flat faces occur. Between σ* and σ**, hopper morphology is expected.Factors controlling the morphology of polyhedral crystals (crystal habit) are analysed, in relation to the factors controlling the morphology of growth spirals, which are related to the roughness of growth steps. It is suggested that the major factors affecting the morphology of polyhedral crystals are phases, solvents, growt temperatures, supersaturations, impurities. It is also suggested that the changes in size of growth unit may drastically modify the morphology of growing crystals.