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Glass blowing

Press Release - 09 February 2009

Scientists crack controversial glass mystery

More than 2,000 years after the discovery of glass, scientists at the University of Bath, in collaboration with the University of Nottingham and the University of California, have got a step closer to solving the mystery of why it behaves like a solid when its molecular structure looks like a liquid.

Their research has been published online in Science Express, in advance of publication in the prestigious journal, Science.

Solids are generally rigid because the molecules fit together in ordered rows, whereas in liquids the molecules are jumbled randomly, allowing the liquid to flow. However, the molecular structure of solid glass looks the same as molten glass, despite being rigid.

Using computer simulations, the researchers were able to test the theoretical process of melting and hardening glass, and believe they are a step closer to understanding a problem that has puzzled physicists for many years.

Dr Robert Jack, from the Department of Physics at the University of Bath, explained: “Snapshots taken with x-rays show that in ice, water molecules fit together in an ordered array, while in liquid water, the molecules are jumbled.

“Scientists can understand why ice is rigid and liquid water is fluid largely from these structural differences.

“Glass, on the other hand, does not offer this explanation because a snapshot of the molecular structure of solid glass is almost indistinguishable from that of the molten liquid - both appear to be jumbled random collections of atoms.

“This observation is at the heart of the problem: if the solid state of glass has a molecular structure just like that of the liquid, how can it be so rigid? Controversy has resulted from the absence of a clear answer to this question.”

Juan Garrahan, Professor of Physics in the School of Physics & Astronomy at the University of Nottingham, added: “By focusing on the ability or inability of molecules to flow we have provided evidence for a new kind of sudden transition between the flowing liquid and the solid glass. This transformation is apparent only when the system is viewed in both space and time.”

The scientists believe their research is a significant step towards new methods for producing glass that is stronger and longer lasting.


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