Fragility of Ge-As-Se glass-forming liquids in relation to rigidity percolation, and the Kauzmann paradox

The concept of mean-field rigidity percolation at average coordination number 〈r〉=2.4 in covalently bonded inorganic glasses is shown to be relevant to the liquid-state behavior of glass-forming chalcogenide systems. In particular it correlates with remarkable variations in ‘‘fragility’’ and excess heat capacity which we observe in the model ternary system Ge-As-Se. Except near ${\mathrm{As}}_2$${\mathrm{Se}}_3$, ${\mathit{T}}_{\mathit{g}}$ itself depends only on 〈r〉 anywhere in the system up to 〈r〉=2.5. These findings provide an important link between key structural concepts of glass science, the relaxation phenomena, and the thermodynamic problem embodied in the Kauzmann paradox.