  The glass-forming ability (GFA) of alloys, colloidal dispersions, and other
particulate materials, as measured by the critical cooling rate $R_c$, can span
more than ten orders of magnitude. Even after numerous previous studies, the
physical features that control the GFA are still not well understood. For
example, it is well-known that mixtures are better glass-formers than
monodisperse systems and that particle size and cohesive energy differences
among constituents improve the GFA, but it is not currently known how particle
size differences couple to cohesive energy differences to determine the GFA. We
perform molecular dynamics simulations to determine the GFA of equimolar,
binary Lennard-Jones (LJ) mixtures versus the normalized cohesive energy
difference $\epsilon_\_$ and mixing energy $\bar \epsilon_{AB}$ between
particles A and B. We find several important results. First, the $\log_{10}
R_c$ contours in the $\bar \epsilon_{AB}$-$\epsilon_\_$ plane are ellipsoidal
for all diameter ratios, and thus $R_c$ is determined by the Mahalanobis
distance $d_M$ from a given point in the $\bar \epsilon_{AB}$-$\epsilon_\_$
plane to the center of the ellipsoidal contours. Second, LJ systems for which
the larger particles have larger cohesive energy are generally better glass
formers than those for which the larger particles have smaller cohesive energy.
Third, $d_M(\epsilon_\_,\bar \epsilon_{AB})$ is determined by the relative
Voronoi volume difference between particles and local chemical order $S_{AB}$,
which gives the average fraction of nearest-neighbor B particles surrounding an
A particle and vice-versa. In particular, the shifted Mahalanobis distance $d_M
- d^0_M$ versus the shifted chemical order $S_{AB}-S_{AB}^0$ collapses onto a
hyperbolic master curve for all diameter ratios.
