title: Ultrahigh-pressure polyamorphism in GeO2 glass with coordination number >6.
abstract: Knowledge of pressure-induced structural changes in glasses is important in various scientific fields as well as in engineering and industry. However, polyamorphism in glasses under high pressure remains poorly understood because of experimental challenges. Here we report new experimental findings of ultrahigh-pressure polyamorphism in GeO2 glass, investigated using a newly developed double-stage large-volume cell. The Ge-O coordination number (CN) is found to remain constant at ∼6 between 22.6 and 37.9 GPa. At higher pressures, CN begins to increase rapidly and reaches 7.4 at 91.7 GPa. This transformation begins when the oxygen-packing fraction in GeO2 glass is close to the maximal dense-packing state (the Kepler conjecture = ∼0.74), which provides new insights into structural changes in network-forming glasses and liquids with CN higher than 6 at ultrahigh-pressure conditions.
authors.affiliation: High Pressure Collaborative Access Team, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, IL 60439; ykono@ciw.edu.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Kono
authors.affiliation: High Pressure Collaborative Access Team, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, IL 60439;
authors.forename: Curtis
authors.initials: C
authors.lastname: Kenney-Benson
authors.affiliation: High Pressure Collaborative Access Team, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, IL 60439;
authors.forename: Daijo
authors.initials: D
authors.lastname: Ikuta
authors.affiliation: Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Aoba-ku, Sendai 980-8578, Japan;
authors.forename: Yuki
authors.initials: Y
authors.lastname: Shibazaki
authors.affiliation: Center for Advanced Radiation Sources, The University of Chicago, Chicago, IL 60637.
authors.forename: Yanbin
authors.initials: Y
authors.lastname: Wang
authors.affiliation: High Pressure Collaborative Access Team, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, IL 60439;
authors.forename: Guoyin
authors.initials: G
authors.lastname: Shen
keywords: glass; high pressure; oxygen packing; polyamorphism