title: Crystal structure of SrGeO3 in the high-pressure perovskite-type phase.
abstract: Single crystals of the SrGeO3 (strontium germanium trioxide) high-pressure phase have been synthesized successfully at 6 GPa and 1223 K. The compound crystallizes with the ideal cubic perovskite-type structure (space group Pm-3m), which consists of a network of corner-linked regular GeO6 octa-hedra (point-group symmetry m-3m), with the larger Sr atoms located at the centers of cavities in the form of SrO12 cubocta-hedra (point-group symmetry m-3m) in the network. The degrees of covalencies included in the Sr-O and the Ge-O bonds calculated from bond valences are 20.4 and 48.9%, respectively. Thus, the Ge-O bond of the GeO6 octa-hedron in the SrGeO3 perovskite has a strong covalency, comparable to those of the Si-O bonds of the SiO4 tetra-hedra in silicates with about 50% covalency. The thermal vibrations of the O atoms in the title compound are remarkably suppressed in the directions of the Ge-O bonds. This anisotropy ranks among the largest observed in stoichiometric cubic perovskites.
authors.affiliation: Graduate School of Science and Engineering, Yamaguchi University, Ube 755-8611, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Nakatsuka
authors.affiliation: Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Arima
authors.affiliation: Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Ohtaka
authors.affiliation: Graduate School of Science and Engineering, Yamaguchi University, Ube 755-8611, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Fujiwara
authors.affiliation: Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Yoshiasa
keywords: crystal structure; high-pressure phase; perovskite; strontium germanate