Understanding the Glass-Forming Ability of Lennard-Jones Mixtures using the Properties of the Interface between the Liquid and Crystal Phases

Amorphous solids form when a liquid is cooled faster than the critical rate R_c, which determines the material’s glass-forming ability and can vary by more than ten orders of magnitude for different alloys. Previous studies have suggested that enhanced glass-forming ability is associated with a higher free-energy barrier for crystallization, originating from the interfacial free energy between the liquid and crystal phases. To understand how interfacial properties influence the crystallization barrier and thus the glass-forming ability, we perform well-tempered metadynamics and molecular dynamics (MD) simulations of liquid–solid coexistence in Lennard-Jones mixtures. We find that the distribution of the local bond-orientational order (BOO) parameter q₆ at fixed global BOO Q₆ obtained from the metadynamics simulations closely matches that from interfacial regions with the same global order in MD simulations of liquid-solid coexistence. This finding allows us to reconstruct the free-energy profile directly from MD simulations of coexistence. These results emphasize that the properties of the interface between the liquid and crystalline phases determine the crystallization free-energy barrier, which in turn governs the glass-forming ability of alloys.