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Why does a gold-silicon mixture near 20 percent silicon form glass more easily than some other gold-silicon mixtures?

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In the gold-silicon system, a mixture containing approximately 20 percent silicon (Au $_{0.8}$ Si $_{0.2}$ ) forms metallic glass more easily than other compositions because it corresponds to a deep cusp in the freezing point curve ( $T_{f}$ ).

To form a glass, a liquid must be cooled from its freezing point ( $T_{f}$ ) to the glass transition temperature ( $T_{g}$ ) without crystallizing. Crystallization is a risk throughout this entire temperature interval. Because the freezing point is significantly lower near the 20 percent silicon composition, the temperature range between $T_{f}$ and $T_{g}$ is much shorter than it is at other compositions. Consequently, the liquid spends less time in the "dangerous" temperature zone where crystallization is likely to occur, allowing the material to be quenched into an amorphous solid more readily.1