Glass Formation Mystery Shattered By Physicists


Physicists from the University of Waterloo have published a paper describing exactly how glass forms on a molecular level, providing an answer to a question that has stumped scientists for years.

The theory, which is very simple, is expected to bring the study of glass to nonexperts, including undergraduates.

"We were surprised – delighted – that the model turned out to be so simple," said James Forrest, a research chair and professor at the Faculty of Science at Waterloo, in the report. "We were convinced it had already been published."

Glass is itself an extremely important part of technology, pharmaceuticals and so on, with glass being defined as much more than the material used to make a window. In fact, any solid that does not have an ordered crystalline structure that forms a molten liquid when heated to a specific temperature is considered a glass.

The theory itself relies on two concepts. One is that of molecular crowding, which essentially describes how molecules in glass move like people in a crowded room. More molecules means that free volume decreases and molecules are restricted in how fast they can move. In a crowded room, people close to the door can move more freely — which is also true of molecules close to the surface of the glass.

The other concept is cooperative movement, tp which the image of a crowded room also applies. Basically, in a crowded room, people rely on the movement of their neighbors to get to where they need to be. In the same sense, molecules in glass cannot move freely, and are instead confined by weak molecular bonds formed with their neighbors.

While both of these concepts aren't anything new, this is the first time they have been combined to describe how a liquid gets turned into a glass.

"Research on glasses is normally reserved for specialists in condensed matter physics," Forrest said. "Now a whole new generation of scientists can study and apply glasses just using first-year calculus."

The theory is applicable to all types of behavior for glass, including surface flow and the once-confusing concept of how glass first gets formed. Indeed, Forrest and his colleagues worked for a huge 20 years on making sure the theory would be compatible with the decades of research already conducted on glass.

The theory will prove especially useful for those trying to understand how glass works at a nanoscale, and will have serious implications for the production of nanomaterials.

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