Kinetics of nucleation in the concentration gradient

The necessity of reconsidering the nucleation theory for the case of the initial stage of reactive diffusion is demonstrated. The existence of sharp concentration gradients and huge diffusion fluxes in the nucleation region changes both the thermodynamics and kinetics of nucleation as well as the very notions of critical nucleus and incubation time. In particular, the incubation period for intermediate phases depends on the diffusivity of the parent phase; nucleation behaviour for the 'total mixing mode' can be non-monotonic; the result of competition of different nucleation modes depends on the ratio of diffusivities in the new and parent phases.