Precise x-ray diffraction measurements using high-energy x rays of synchrotron radiation and systematic Raman scattering measurements were carried out for GexS100−x (10 ⩽ x ⩽ 40) network glasses. The structural models of the network glasses were proposed based on the results. In the stoichiometric composition Ge33S67, GeS4 tetrahedral units are connected forming either corner-sharing or edge-sharing structures. In the S-rich glasses, S atoms are inserted between two neighboring GeS4 tetrahedra, resulting in a flexible floppy network. In a much more S-rich region, some S8 ring molecules are isolated from the network, and assemble to form a crystal in nanoscopic scale. In this respect, Ge10S90 samples are regarded as crystallized glasses. In the Ge-rich region, the GeS4 tetrahedra are connected with bridging Ge atoms. The connection makes a new rigid network. The bridging Ge-S bond is weaker than the intratetrahedron bond, and this leads to drastic changes in the optical properties.
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Y. Sakaguchi, T. Hanashima, K. Ohara, Al-Amin A. Simon, & M. Mitkova. (2019). Structural Transformation in GexS100−x (10 ≤ x ≤ 40) Network Glasses: Structural Varieties in Short-Range, Medium-Range, and Nanoscopic Scale. Physical Review Materials, 3(3), 035601. doi: 10.1103/PhysRevMaterials.3.035601
Sakaguchi, Y.; Hanashima, T.; Ohara, K.; Simon, Al-Amin A.; and Mitkova, M.. (2019). "Structural Transformation in GexS100−x (10 ≤ x ≤ 40) Network Glasses: Structural Varieties in Short-Range, Medium-Range, and Nanoscopic Scale". Physical Review Materials, 3(3), 035601-1 - 035601-18. http://dx.doi.org/10.1103/PhysRevMaterials.3.035601