  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.
