Barrier-Free Nucleation at Grain-Boundary Triple Junctions During Solid-State Phase Transformations

Molecular dynamics simulations are used to provide strong evidence for barrier-free nucleation events in a heterogeneous solid-solid system. The barrier-free events are characterized by an absence of an incubation time and a growth rate of the emerging phase that is independent of the system size. Furthermore, an analysis of the size and shape of the critical nucleus using the Winterbottom construction indicates that no solution exists for these barrier-free cases. We propose that barrier-free nucleation, which will have a profound effect on phase transformation kinetics, may be a general phenomenon for any polycrystalline material.