Nucleation in nanostructures: Effects of embryo loss

Abstract

Conventional nucleation theory considers only the growth and decay of embryos by single atom addition or subtraction. The numerous processes involved in mechanical alloying, such as creation and movement of dislocations and point defects, and passage of thermal and stress waves, could readily destroy a subcritical embryo which typically contains at most only a few tens of atoms. This paper modifies the nucleation equation to account for such embryo loss, and solves the resulting equation analytically in the steady state approximation. The effects of embryo loss are described by several dimensionless groupings of kinetic and thermodynamic parameters. Embryo loss is found significant only if the probability of destruction is comparable to or greater than the probability of growth by single atom capture. The effects of embryo loss are greatest for phases which form with large critical nuclei or complex unit cells.