Crystallization Instability in Glass-Forming Mixtures

Understanding the mechanisms by which crystal nuclei form is crucial for many phenomena such as gaining control over crystallization in glass-forming materials or accurately modeling rheological behavior of magma flows. The microscopic nature of such nuclei makes understanding hard in experiments, while computer simulations are hampered by short timescales and small system sizes. Here we use GPU simulations to reveal a general nucleation mechanism in mixtures. We find that the supercooled liquid of a prized model glass former is inherently unstable to crystallization, i.e., that nucleation is unavoidable on the structural relaxation timescale, for sufficient system sizes. This is due to compositional fluctuations leading to regions composed of one species which rapidly crystallize. This mechanism provides a minimum rate of nucleation in mixtures in general, and we show that it pertains to the metallic glass former copper zirconium.

Ingebrigsten et al. Phys. Rev. X 9, 031016 (2019)