Structure of Na2S–GeS2 glasses studied by using neutron and X-ray diffraction and reverse Monte Carlo modeling

Neutron and X-ray diffraction measurements were performed to investigate the structure of Na2S–GeS2 glasses synthesized by mechanical alloying. The Ge–S coordination numbers calculated from the total correlation functions show that GeS4 tetrahedra form the basic framework structure of Na2S–GeS2 glasses. In addition, a three-dimensional structural model of the (Na2S)50(GeS2)50 glass was obtained by using reverse Monte Carlo (RMC) simulation on neutron and X-ray diffraction data, and it was compared with the RMC model previously obtained for a (Li2S)50(GeS2)50 glass. The results show that the Ge–S framework structures in the two glasses are almost the same in the short and intermediate ranges; that is, the Ge–S framework structures are formed mainly by the connection of corner-sharing GeS4 tetrahedra. Many of the Na ions are coordinated by four S atoms, which are non-bridging S atoms and/or bridging S atoms.