1. Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, USA
   
2. Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850, USA
   
3. J. Nehru Centre for Advanced Scientific Research, Jakkur Campus, Bangalore 560064, India

Correspondence to: C. A. Angell¹ Correspondence and requests for materials should be addressed to C.A.A. (Email: caa@asu.edu).

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 made³; 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 study⁵ 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.