Ergodicity failure near structural glass transformations

Relaxation timescale, for glass-forming materials is analyzed within a self -consistent description introduced within percolation theory treatment of t he Adam-Gibbs model. The ergodic-non-ergodic phase diagram is proposed for the case of molecular supercooled liquids in terms of the ergodic-phase ins tability temperature T-E vs fragility. T-E, being below and close to the gl ass-transformation temperature T-g, is established through violation of the ergodic, hypothesis, i.e. by a crossover from the Gaussian ('ergodic') to a non-Gaussian dynamics of evolution of clusters. The finite-size fractal c luster distribution is deduced from the known Stauffer scaling form. Crosso ver of the compact-structure ('ergodic') clusters to the hole-like glassy c lusters is attributed to their critical-size thermal fluctuations. (C) 2001 Published by Elsevier Science Ltd.