Generalized theory of nucleation kinetics. III. Nucleation in dilute systems and/or in systems with a limited number of effective single elements

Abstract

The kinetic theory of nucleation has been modified by dropping out the implicit assumption that the molar fraction of single structural elements (atoms, molecules) participating in cluster formation is close to unity. The concentration of effective single elements CH (controlled by dilution of the system or by introducing restrictions to the formation of clusters) strongly affects critical conditions of the phase transition, critical cluster size, and steady‐state nucleation rates. The extended theory can be obtained from the classical equations if the free energy of a cluster composed of g single elements, ΔF (g) is replaced by Δ? (g) =ΔF (g) −kT ln(CH) g, the additional term being related to the change in the mixing entropy of effective single elements (CH) with (1−CH) ineffective structural units. The revised theory can be applied to transitions in multicomponent systems and systems composed of asymmetric orientable elements, like liquid crystals, polymers etc.