Glass formation at the limit of insufficient network formers

Kohara, Shinji*; Suzuya, Kentaro; Takeuchi, Ken*; Loong, C.-K.*; Grimsditch, M.*; Weber, J. K. R.*; Tangeman, J. A.*; Key, T. S.*

Inorganic glasses normally exhibit a network of interconncted covalent-bonded structural elements that has no long-range order. In silicate glasses the network formers are based on SiO-tetrahedra interconnected via oxygen atoms at the corners. Conventional wisdom then implies that alkaline and alkaline-earth orthosilicate materials cannot be vitrified because they do not contain sufficient network forming SiO to establish the needed interconnectivity. We have studied a bulk magnesium orthosilicate glass obtained by containerless melting-and-cooling. We find that the role of network former is largely taken on by corner- and edge-sharing of highly distorted ionic Mg-O species that adopt 4-, 5- and 6-coordination with oxygen. The results suggest that similar novel glassy phases may be found in the containerless environment of interstellar space.