The design of multifunctional bulk metallic glasses is limited by the lack of a quantitative understanding of the variables that control the glass-forming ability of alloys. Both geometric frustration (e. g., differences in atomic radii) and energetic frustration (e. g., differences in the cohesive energies of the atomic species) contribute to the glass-forming ability. We perform molecular dynamics simulations of binary Lennard-Jones mixtures with only energetic frustration. We show that there is little correlation between the heat of mixing Delta H-mix and critical cooling rate R-c, below which the system crystallizes, except that Delta H-mix < 0. By removing the effects of geometric frustration, we show strong correlations between R-c and the variables epsilon = (epsilon(BB) - epsilon(AA))/(epsilon(AA) + epsilon(BB)) and <(epsilon)over bar>(AB) = 2 epsilon(AB)/(epsilon(AA) + epsilon(BB)), where epsilon(AA) and epsilon(BB) are the cohesive energies of atoms A and B and epsilon(AB) is the pair interaction between A and B atoms. We identify a particular composition-dependent combination of epsilon-and (epsilon) over bar (AB) that collapses the data for R-c over nearly 4 orders of magnitude in cooling rate. By performing local structural analyses, we find that energetic frustration, even in the absence of geometric frustration, can induce short-range fivefold symmetric order that impedes crystallization. This result emphasizes that energetic frustration plays an important role in determining the glass-forming ability, and thus it should be taken into account in the design of new metallic glass formers.
