Creating a glass is akin to racing against a thermodynamic clock. The clock begins ticking when a liquid is cooled below its melting temperature TM. Typically, as the supercooled liquid’s temperature decreases, so do its enthalpy and volume, as illustrated by the plot in figure 1a. (Water, which has a negative thermal expansion coefficient below 4 °C, is a notable exception.) At what’s known as the glass transition temperature TG, the atoms in the liquid become so tightly packed that they can no longer easily rearrange themselves. In that glassy state, the system behaves like a solid, although liquid-like disorder is “frozen” into its structure. The challenge, then, is to supercool the liquid from TM to TG so fast that there’s no chance for a crystalline phase to nucleate and grow.

In materials that form localized chemical bonds—polymers, organics, and silica, to name...

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