Résumé
We present a study of the structural properties of (x)Na $_2$ S-(1-x)GeS $_2$glasses through DFT-based molecular dynamics simulations, at different sodium concentrations ( $0<x<0.5$ ). We computed the radial pair correlation functions as well as the total and partial structure factors. We also analyzed the evolution of the corner- and edge-sharing intertetrahedral links with the sodium concentration and show that the sodium ions exclusively destroy the former. With the increase of the sodium concentration the ``standard'' FSDP disappears and a new pre-peak appears in the structure factor which can be traced back in the Na-Na partial structure factor. This self organization of the sodium ions is coherent with Na-rich zones that we find at high modifier concentration.