Short range order and topology of binary Ge-S glasses

Short range order and topology of GexS100-x glasses over a broad composition range (20 <= x <= 42 in at%) was investigated by neutron diffraction, X-ray diffraction, and Ge K-edge extended X-ray absorption fine structure (EXAFS) measurements. The experimental data sets were fitted simultaneously in the framework of the reverse Monte Carlo simulation method. It was found that both constituents (Ge and S) satisfy the Mott-rule in all investigated glasses: Ge and S atoms have 4 and 2 neighbours, respectively. The structure of these glasses can be described with the chemically ordered network model: Ge-S bonds are preferred; S-S bonds are present only in S-rich glasses. Dedicated simulations showed that Ge-Ge bonds are necessary in Ge-rich glasses. Connections between Ge atoms (such as edge-sharing GeS4/2 tetrahedra) in stoichiometric and S-rich glasses were analysed. The frequency of primitive rings was also calculated. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Short range order and topology of GexS100-x glasses with a composition range of 20 <= x <= 42 at% were investigated using neutron diffraction, X-ray diffraction, and Ge K-edge extended X-ray absorption fine structure (EXAFS) measurements. The experimental data sets were analyzed using the reverse Monte Carlo simulation method. It was observed that both Ge and S atoms in the glasses satisfied the Mott-rule, with Ge and S atoms having 4 and 2 neighbors, respectively. The chemically ordered network model described the structure of these glasses, with Ge-S bonds being preferred and S-S bonds only present in S-rich glasses. Ge-Ge bonds were found to be necessary in Ge-rich glasses, and the connections between Ge atoms, such as edge-sharing GeS4/2 tetrahedra, were analyzed. The frequency of primitive rings was also calculated.