Short range order and Ag diffusion threshold in Agx(Ge0.25Se0.75)100−x glasses


  • Dedicated to Stanford R. Ovshinsky on the occasion of his 90th birthday


A structural investigation of Agx(Ge0.25Se0.75)100 − x glasses with x = 5, 15, and 25 at.% has been carried out by neutron diffraction and ab initio molecular dynamics (AIMD) simulation. A structural model for the glasses has been proposed: the Ge(Se1/2)4 tetrahedra would remain the fundamental structural units in all samples. The introduction of Ag in the Ge0.25Se0.75 network would lead to a decrease in homopolar Se[BOND]Se bonds and appearance of Ge[BOND]Ge bonds. A strong evolution in the Ag[BOND]Ag correlations upon introduction of Ag was observed with the Ag[BOND]Ag correlation distances changing from 4.4 Å for the Ag-poor glass to 3.0 Å for the Ag-rich ones. Such information was used to discuss the evolution of conductivity with Ag content in these glasses.