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 As2Se3, Tg 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. © 1990 The American Physical Society.