Application of the bond valence method to reverse Monte Carlo produced structural models of superionic glasses - art. no. 024204

The reverse Monte Carlo RMC method has shown to be a useful tool for extrac ting structural properties from diffraction data of disordered systems, suc h as ion-conducting glasses. In this paper we investigate ion conduction in Ag-based superionic glasses by simple random-walk simulations based on the bond-valence information present in the RMC-produced structural models. Us ing this method we are able to explore the ion-conduction pathways and to c alculate the ionic conductivity on a quantitative basis. The migration path ways are assumed to be the regions of the structural models where the valen ce mismatch for the mobile ion remains below a threshold value. The results for the AgI-doped glasses show that there are no long-range migration path ways for Ag sites in an entire iodine environment. Rather, the Ag+ ions are generally moving between sites with a mixed oxygen-iodine coordination. Th e method is able to predict the ionic conductivity of highly AgI-doped supe rionic glasses, but tends to overestimate the conductivity of undoped glass es (with cr < 10(-5) <Omega>(-) cm(-1)) and underestimate the conductivity of highly conducting crystalline alpha -AgI. The discrepancies for these ma terials are discussed, as well as the possibility and limitations of using a similar approach to study the frequency dependence of the conductivity.