Mechanistic understanding of the effect of rigidity percolation on structural relaxation in supercooled germanium selenide liquids

High-resolution 77Se nuclear magnetic resonance spectroscopy is used to investigate the rotational dynamics of Se atoms in GexSe100-x supercooled liquids with 5≤x≤23. The Se atoms in Se-Se-Se linkages are found to be significantly more mobile compared to those in Ge-Se-Se/Ge linkages. The time scale of the rotational dynamics of Se-Se-Se linkages and its temperature dependence are nearly identical for liquids with x≤17 but the time scale displays an abrupt increase for the liquids with x=20 and 23, at and above the rigidity percolation threshold. Such a dynamical transition is shown to be consistent with a sudden elastic stiffening of the atomic network of GexSe100-x supercooled liquids at the percolation threshold.