Abstract
Analysis is presented of photon correlation spectroscopy measurements in fragile orthoterphenyl and strong boron trioxide glass-forming liquids. The measured dynamic structure factor of these liquids is found to result from a bimodal distribution of relaxation times (fast and slow). Furthermore, the amplitude of the slower decay in the structure factor is attributed to the volume fraction of slowly relaxing material in the liquid. A correlation between this amplitude and the fragility of the glass-forming liquid is demonstrated. Examined in light of percolation concepts, this correlation leads us to propose that the distinction between strong and fragile behavior is directly related to volume fraction of slow material in the liquid.