Atomic level structure of Ge-Sb-S glasses: Chemical short range order and long Sb-S bonds

• Published in: Journal of alloys and compounds 2019-02, Vol.774, p.1009-1016
• Main Authors: Pethes, I., Nazabal, V., Ari, J., Kaban, I., Darpentigny, J., Welter, E., Gutowski, O., Bureau, B., Messaddeq, Y., Jóvári, P.
• Format: Article
• Language: English
• Subjects: Atomic structure; Chalcogenide glasses; Chemical compounds; Chemical Sciences; Composition; Computer simulation; Covalent bonds; Diffraction; EXAFS; Fine structure; Ge-Sb-S; Glass; Monte Carlo simulation; Neutron diffraction; Organic chemistry; Raman spectra; RMC; Short range order; Structure; X ray absorption; X-ray diffraction
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2018.09.334

The structure of Ge20Sb10S70, Ge23Sb12S65 and Ge26Sb13S61 glasses was investigated by neutron diffraction (ND), X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS) measurements at the Ge and Sb K-edges as well as Raman scattering. For each composition, large scale structural models were obtained by fitting simultaneously diffraction and EXAFS data sets in the framework of the reverse Monte Carlo (RMC) simulation technique. Ge and S atoms have 4 and 2 nearest neighbors, respectively. The structure of these glasses can be described by the chemically ordered network model: Ge-S and Sb-S bonds are always preferred. These two bond types adequately describe the structure of the stoichiometric glass while S-S bonds can also be found in the S-rich composition. Raman scattering data show the presence of Ge-Ge, Ge-Sb and Sb-Sb bonds in the S-deficient glass but only Ge-Sb bonds are needed to fit diffraction and EXAFS datasets. A significant part of the Sb-S pairs has 0.3–0.4 Å longer bond distance than the usually accepted covalent bond length (∼2.45 Å). From this observation it was inferred that a part of Sb atoms have more than 3 S neighbors. •Structural models of GeSbS glasses consistent with multiple datasets are constructed.•Structure of these glasses can be described by the chemically ordered network model.•Ge and S atoms obey the Mott-rule and have 4 and 2 nearest neighbors, respectively.•Long Sb-S bonds were observed, suggesting that SbS5 units may exist in this system.