Ageing, fragility and the reversibility window in bulk alloy glasses

Non-reversing relaxation enthalpies (DeltaH(nr),) at glass transitions T-g(x) in the P(x)Ge(x)Se1(1-2x) ternary display wide, sharp and deep global minima (similar or equal to0) in the 0.09 < x < 0. 145 range, within which T(g)s become thermally reversing. In this reversibility window, glasses are found not to age, in contrast to ageing observed for fragile glass compositions outside the window. Thermal reversibility and lack of ageing seem to be paradigms of self-organization which molecular glasses share with protein structures which repetitively and reversibly change conformation near T-g and the folding temperature respectively.