LAUSR

While the role of the free energy barrier during nucleation is a text-book subject the importance of the kinetic factor is frequently underestimated. We obtained both quantities from molecular dynamics (MD) simulations for the pure Ni and B2 phases in the Ni50Al50 and Cu50Zr50 alloys. The free-energy barrier was found to be higher in Ni but the nucleation rate is much lower in the Ni50Al50 alloy which was attributed to the ordered nature of the B2 phase. Since the Cu50Zr50 B2 phase can has even smaller fraction of the anti-site defects its nucleation is never observed in the MD simulation.