Aging, Fragility and Reversibility Window in Bulk Alloy Glasses

Non-reversing relaxation enthalpies (∆H nr) at glass transitions T g (x) in the P x Ge x Se 1-2x ternary display a wide, sharp and deep global minimum (~0) in the 0.09 < x < 0.145 range, within which T g becomes thermally reversing. In the reversibility window these glasses are found not to age, in contrast to aging observed for fragile glass compositions outside the window. Thermal reversibility and lack of aging are paradigms that molecular glasses in the window share with proteins in transition states, which result from structural self-organization in both systems. In proteins the self-organized structures appear to be at places where life sustaining repeating foldings and unfoldings occur. Aging occurs in many materials, both organic and inorganic. Inorganic crystals age under electrical, mechanical, or thermal stresses, often as a result of dislocation motion.