Computational studies of the glass-forming ability of binary alloys

Some alloys easily form glasses, while others do not. The critical cooling rates of good versus poor glass-formers can differ by more than 14 orders of magnitude. An important, open problem is to identify the elemental features that give rise to this wide variation in the glass-forming ability of alloys. In recent studies, we have performed large-scale molecular dynamics simulations of Lennard-Jones and patchy-particle models of alloys to determine how several elemental features, such as the cohesive energy, atomic size ratio, and symmetry of the atomic bonds, affect glass formation in binary alloys. We find that combinations of features that give rise to local icosahedral order possess good glass-forming ability. In addition, chemical frustration, characterized by the degree to which the local concentration of different atomic species deviates from that in the liquid state, strongly enhances the glass-forming ability. We also identify a new mechanism of “bond shortening” for improving the glass-forming ability, where atomic species with weaker repulsive interactions are closer to each other than the other atom types are to each other. These findings for binary alloys can also be used to guide glass design in ternary and multicomponent alloys.