Glass-forming particles go all exotic

For thousands of years, humans have been entranced by the unique beauty and physical properties of glass, producing jewelry, containers and tools from the material. However, the physics underlying the phenomenon of glass formation remains surprisingly complex.

Now, in paper in Nature Communications, researchers from the Institute of Industrial Science at the University of Tokyo in Japan report using a numerical simulation to uncover new insights on the formation of glass from particles of varying sizes. They found a new type of compositional ordering, consisting of patterns with small and large particles, which could affect the chance of glass forming correctly or becoming partially ordered.

Glass is neither a free-flowing liquid nor an orderly, structured crystalline solid. Instead, it is a ‘metastable supercooled state’, in which a liquid has been cooled so quickly that its constituent particles do not have enough time to rearrange themselves but rather are ‘frozen’ in a disordered configuration. However, the conditions under which particles from an ideal glass, rather than undergoing crystallization or phase separation, remain obscure. A better understanding is needed to improve the physical properties of glassy materials, including smart-device screens.

In recent years, a specialized model liquid has been developed to achieve a deeply supercooled state, allowing researchers to study its properties without interference from crystallization or phase separation. This model liquid has gained popularity in the scientific community. To gain a better understanding of its characteristics, the researchers turned to computer simulations.

Unexpectedly, these simulations revealed that unconventional structural arrangements – such as connections between small and large particles, and patches formed by medium-sized particles – can significantly influence the ultimate behavior of the material during the cooling process. The researchers tracked the ‘coordination number’ of the particles, which measures how many neighbors each particle is touching. This allowed them to identify novel patterns of small and large particles.

“The observed network-like structure we saw was unusual and has not been reported in previous studies. We called this unconventional pattern ‘exotic compositional order,’” says lead author Hua Tong.

The researchers found that such exotic compositional ordering has an unusual impact on structural relaxation dynamics. “Our results raise doubts about whether this model liquid can be considered an ideal glass-forming liquid,” explains senior author Hajime Tanaka.

The findings of this study have the potential to contribute to the development of an ideal model liquid, specifically designed to explore the fundamental nature of glass transition.

This story is adapted from material from the University of Tokyo, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.