New method to measure the fragility of liquid

The study makes the physics of glass formation clearer.


The fragility of liquid is how the fluidity of a liquid changes with temperature. It is believed to be one of the key properties of a liquid. A low fragility is believed to promote the formation of metallic glasses. Yet, the fragility remains poorly understood since experimental data on its compositional dependence are scarce.

Measuring the fragility of a wide range of metallic glass-forming liquids is quite difficult. But, scientists from Yale University have developed a method to measure how the fluidity of a liquid changes with temperature. The method called the film inflation method (FIM) measures the fragility of a wide range of metallic glass-forming liquids.

The method allows scientists to get a clearer sense of the liquids’ properties. At the same time, it denies the long-held assumption in the field that a low fragility is better for forming metallic glasses.

These materials’ peculiar atomic structures are responsible for their properties; as metallic glasses cool from a liquid to a solid, their atoms arrange themselves at random rather than crystallizing as ordinary metals do.

Jan Schroers, professor of mechanical engineering & materials science, said“The method is a “big step toward” figuring out the tricky physics of metallic glass. The liquid part of the formation process is especially confounding.”

“The liquid state is the most difficult state for us to understand, to measure. Essentially everything is known about solids, how the atoms arrange, and we can calculate it all on a computer – you almost don’t need to do experiments anymore. Gas is also very easy because the atoms are so far apart from each other that they don’t interact. Liquid, as a state, we almost know nothing about it.”

“This allows us to extend theories on glass formation, which is one of the biggest mysteries in physics.”

Journal Reference:

  1. Kube, S.A., Sohn, S., Ojeda-Mota, R. et al. Compositional dependence of the fragility in metallic glass-forming liquids. Nat Commun 13, 3708 (2022). DOI: 10.1038/s41467-022-31314-3
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