Physical properties of the Ge_xSe_1-x glasses in the 0<x<0.42 range in correlation with their structure

Physical properties, including mechanical, thermal and optical properties, have been investigated for chalcogenide glasses in the Ge_xSe _1-x system, for x ranging between 0 and 0.42. In the 0<x<1/3 range, the elastic moduli and the glass transition temperature (T_g) evolve as would be expected from the chain crossing model or from the clustering model. The change is continuous and there is no incidence of the rigidity percolation threshold (〈r〉=2.4). Conversely, the chemical threshold (〈r〉=2.67) clearly induces a change in the compositional trend of these properties. In the x > 1/3 range, T_g decreases and the elastic moduli markedly increase, which is not expected from the continuously reticulated model. The change of the physical properties in this range is an indicator of the existence of separated Ge-rich domains.