A new way of making glass

When cooling a liquid below its melting temperature it either crystallizes or transforms into a glass.  Glass is a peculiar state of matter: it has the mechanical properties of a solid but an amorphous structure like a liquid.

As long ago as 1952, Sir Charles Frank at the University of Bristol

Making glass by changing the structure of a liquid. Left: normal liquid alloy of nickel (silver) and phosphorous (orange) atoms.  Encouraging atoms to form bicapped square antiprisms (inset) turned the liquid into a solid glass (right) where the nickel (turquoise) and phosphorous (green) atoms in antiprisms are drawn larger

Although such motifs have very recently been found in

The Düsseldorf and Bristol researchers created a new type of glass in a computer through encouraging atoms in a nickel-phosphorous alloy to form the pictured polyhedron.  When these polyhedra formed, the liquid no longer flowed – it had become a solid. In other words, they found that instead of cooling, a liquid can turn into a glass by changing its structure.

Dr Paddy Royall of the University of Bristol said: "The method we developed employed computer simulations of liquids, performed on the University of Bristol's BlueCrystal supercomputer, where the atoms were driven to form more polyhedra.

"Although many more polyhedra were formed, the atomic arrangements were still disordered rather than a periodic arrangement as seen in crystals.  This means that the solid that was formed had to be a glass."

Dr Thomas Speck of Heinrich-Heine-Universität, Düsseldorf said: "These results mean that structure can control whether a material is liquid or solid and thus open the way to design new glasses: for example metallic glasses whose great lightness and strength promise exciting applications and chalcogenide glasses which are used in memory applications and phase switch memory, a possible future technology for data storage."

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