Silver environment and covalent network rearrangement in GeS3-Ag glasses

The structure of Ag-doped GeS3 glasses (0, 15, 20, 25 at.% Ag) was investigated by diffraction techniques and extended x-ray absorption fine structure measurements. Structural models were obtained by fitting the experimental datasets simultaneously by the reverse Monte Carlo simulation technique. It is observed that Ge has mostly S neighbours in GeS3, but Ge-Ge bonds appear already at 15% Ag content. Sulfur has ~2 S/Ge neighbours over the whole concentration range, while the S-Ag coordination number increases with increasing Ag content. Ag-Ag pairs can already be found at 15% Ag. The Ag-S mean coordination number changes from 2.17 +/- 0.2 to 2.86 +/- 0.2 between 15% and 25% Ag content. Unlike the As-S network in AsS2-25Ag glass, the Ge-S network is not fragmented upon Ag-doping of GeS3 glass.