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DF: Fachverband Dielektrische Festkörper

DF 5: Glass I (joint session with DY)

DF 5.6: Vortrag

Dienstag, 27. März 2007, 11:30–11:45, H23

Understanding the fragility of supercooled liquids in terms of the properties of the potential energy landscape — •Andreas Heuer — Inst. f. Phys. Chemie, Corrensstr. 30, 48149 Münster

According to the Angell representation supercooled liquids are classified according to their fragility, i.e. the degree of non-Arrhenius behavior. Although in recent years fragility has been empirically correlated with different properties such as, e.g., mechanical behavior no microscopic understanding of the fragility exists. We report computer simulations of different glass-forming systems (silica, binary Lennard-Jones) where a detailed characterization of the potential energy landscape has been achieved. A crucial parameter is the crossover energy scale above which the local dynamics is fluid-like and below which it becomes activated. For these systems the macroscopic diffusion constant can be analytically expressed in terms of landscape parameters, reflecting its thermodynamic properties and its local dynamics. In this way we can show that the fragility strongly depends on the crossover energy scale and that for fragile systems the crossover to activated behavior only starts for very low-energy configurations. This result is interpreted in qualitative terms.