Single-crystal neutron diffraction study of the fast-ion conductor β-Ag 2S between 186 and 325°C

Abstract

Partial Fourier synthesis of the silver ion density in bcc β-Ag 2S at several temperatures reveals cation delocalization in bands along 〈100〉. This density may be analytically represented by use of higher-rank tensors, with partial occupancy of both octahedral and tetrahedral interstices below 200°C, but only tetrahedral occupancy at higher temperatures. R values range from 2.6 to 5.9%. The distribution of mobile ions differs greatly in α-AgI and β-Ag 2S, despite similar anion arrays, reflecting the different silver ion concentrations and characteristics of the bonding present in the respective low-temperature phases.