Vitrification of a monatomic metallic liquid

Although the majority of glasses in use in technology are complex mixtures of oxides or chalcogenides, there are numerous examples of pure substances - 'glassformers' - that also fail to crystallize during cooling. Most glassformers are organic molecular systems, but there are important inorganic examples too(1,2), such as silicon dioxide and elemental selenium ( the latter being polymeric). Bulk metallic glasses can now be made(3); but, with the exception of Zr50Cu50 ( ref. 4), they require multiple components to avoid crystallization during normal liquid cooling. Two-component 'metglasses' can often be achieved by hyperquenching, but this has not hitherto been achieved with a single- component system. Glasses form when crystal nucleation rates are slow, although the factors that create the slow nucleation conditions are not well understood. Here we apply the insights gained in a recent molecular dynamics simulation study(5) to create conditions for successful vitrification of metallic liquid germanium. Our results also provide micrographic evidence for a rare polyamorphic transition preceding crystallization of the diamond cubic phase.