Structural study of AsS2–Ag glasses over a wide concentration range

(As0.33S0.67)100-xAgx (0 ≤ x ≤ 28) bulk glasses showing micro-phase separation in a wide concentration range have been studied by X-ray diffraction, neutron diffraction and extended X-ray absorption fine structure measurements. The AsAgS2 composition, which forms a homogeneous glass, is modeled with the reverse Monte-Carlo simulation technique. It is established that Ag prefers the environment of S; Ag―As bonding cannot be observed. Similarly to the AsAgS2 crystalline modifications smithite and trechmannite, the main structural units of the glass are AsS3 pyramids. The covalent network of As and S atoms becomes fragmented in the glassy AsAgS2 unlike in the glassy AsS2. The environment of Ag atoms in the AsAgS2 glass differs from that in the crystalline state. In average, each Ag atom has four nearest neighbors, three of them being S and one being Ag.

► AsS3 pyramids are the main structural units of the AsAgS2 glass.
► Covalent network of As and S atoms is fragmented in the glassy AsAgS2.
► Environment of Ag atoms in glassy AsAgS2 differs from that in the crystalline state.