Local motifs in GeS₂–Ga₂S₃ glasses

The structure of (GeS₂)_0.75(Ga₂S₃)_0.25 and (GeS₂)_0.83(Ga₂S₃)_0.17 glasses was investigated by Raman scattering, high energy X-ray diffraction and extended X-ray absorption fine structure (EXAFS) measurements at the Ga and Ge K-edges. The reverse Monte Carlo simulation technique (RMC) was used to obtain structural models compatible with diffraction and EXAFS datasets. It was found that the coordination number of Ga is close to four. While Ge atoms have only S neighbors, Ga binds to S as well as to Ga atoms showing a violation of chemical ordering in GeS₂–Ga₂S₃ glasses. Analysis of the corner- and edge-sharing between [GeS_4/2] units revealed that about 30% of germanium atoms participate in the edge-shared tetrahedra. - Highlights: • Structural models of GeS₂–Ga₂S₃ glasses consistent with XRD + EXAFS data are created. • Chemical order is respected but Ga–Ga bonds are present caused by S-deficiency. • The coordination number of Ga is 3.7 ± 0.3. • The frequency and geometry of corner/edge-sharing [GeS_4/2] units were determined.