Kinetics of nucleation in the concentration gradient

The necessity of reconsidering the nucleation theory for the case of the in itial stage of reactive diffusion is demonstrated. The existence of sharp c oncentration gradients and huge diffusion fluxes in the nucleation region c hanges both the thermodynamics and kinetics of nucleation as well as the ve ry notions of critical nucleus and incubation time. In particular, the incu bation period for intermediate phases depends on the diffusivity of the par ent phase; nucleation behaviour for the 'total mixing mode' can be non-mono tonic; the result of competition of different nucleation modes depends on t he ratio of diffusivities in the new and parent phases.