title: Structural changes of quartz-type crystalline and vitreous GeO2 under pressure.
abstract: Using a large volume high pressure apparatus, quartz-type crystalline GeO2 and Li2O-4GeO2 glass have been compressed up to 14 GPa at room temperature and their local structural changes have been investigated by an in-situ XAFS method. In quartz-type crystalline GeO2, the change of the coordination number from 4 to 6 begins above 8 GPa and finishes below 12 GPa. On decompression, reversal transition begins below 8 GPa and there is a large hysteresis. Almost no sixfold coordination of Ge is preserved after releasing pressure. Change of coordination number in vitreous Li2O-4GeO2 begins above 6 GPa and is completed below 10 GPa. Reversal transition begins below 10 GPa and the hysteresis is smaller than that of quartz-type GeO2. Change of coordination number in vitreous Li2O-4GeO2 is also reversal.
authors.affiliation: Earth and Space Science, Osaka University, Toyonaka, Japan. ohtaka@ess.sci.osaka-u.ac.jp
authors.forename: O
authors.initials: O
authors.lastname: Ohtaka
authors.forename: A
authors.initials: A
authors.lastname: Yoshiasa
authors.forename: H
authors.initials: H
authors.lastname: Fukui
authors.forename: K I
authors.initials: KI
authors.lastname: Murai
authors.forename: M
authors.initials: M
authors.lastname: Okube
authors.forename: Y
authors.initials: Y
authors.lastname: Katayama
authors.forename: W
authors.initials: W
authors.lastname: Utsumi
authors.forename: Y
authors.initials: Y
authors.lastname: Nishihata