Local- and Intermediate-Range Order in Room Temperature Superionic Conducting Ag-GeSe₃ Glasses

Abstract

Local-and intermediate-range atomic order in Ag ion conducting glasses Ag x (GeSe 3 ) 1−x with x = 0.15, 0.28, 0.33, and 0.50 were investigated by combining anomalous X-ray scattering (AXS), X-ray and neutron diffraction (XRD and ND), and reverse Monte Carlo (RMC) modeling. By adding the ND pair distribution function to AXS and XRD results, reasonable partial structure factors and partial pair distribution functions were obtained. In contrast to the previous AXS and RMC study, significant Ag-Ge and Ge-Ge correlations are observed in the first coordination shell, which is consistent with an ab initio molecular dynamics simulation. The coordination numbers around the Ge and Se mostly follow the 8− N rule over all Ag concentrations if Ag ions are not taken into account. With increasing the Ag concentration, the number of Ge and Se atoms around Ag increase remarkably, while the Ag-Ag coordination number increases only slightly. This indicates that the Ag conducting path is formed through the second neighbor Ag-Ag correlations.