Deciphering the glass conundrum

Scientists believe they are a step closer to understanding the glass transition phenomenon – when a liquid becomes a solid without freezing.

Previous theories behind amorphous solids, those without definite geometric or crystalline shapes, still vary widely. A group of researchers from universities in Bristol and Mainz, Germany may have found a way to unite the differing interpretations.

Just what is glass?

Dr Paddy Royall, from the University of Bristol, said: “The challenge boils down to whether glass is a true solid in its own right – the so-called thermodynamic interpretation – or whether in essence glass is ‘just’ a very viscous liquid, albeit with a viscosity so large that pouring a ‘glass’ of glass would take around a million times the age of the universe – the so-called dynamic interpretation."

In the thermodynamic interpretation, with the right amount of cooling, an unusual material called the ‘ideal glass’ would form. This glass, similar to a crystal, only has one way to organise its atoms, but oddly, is amorphous and disordered. Although it is not completely understood how there can be only one way to arrange atoms in a disordered material, measurements made by the scientists indicate their real life samples are very close to the ideal glass.

Dr Royall said: “The dynamical interpretation of the glass transition seems to end at a ‘critical point’, which is close to, or even coincides with, the temperature at which the ideal glass is formed. In other words, the dynamical and thermodynamic interpretations of the glass transition are different reflections of the same underlying phenomenon."

The paper was published in Physical Review X.