Journal
JOURNAL OF CHEMICAL PHYSICS
Volume 131, Issue 16, Pages -Publisher
AIP Publishing
DOI: 10.1063/1.3243854
Keywords
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Funding
- Corning Incorporated
- Honda R D Co. Ltd.
- NSF TeraGrid [DMR 080064, DMR 090073, DMR 090079]
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A recently developed atomistic method capable of calculating the fragile (non-Arrhenius) temperature behavior of highly viscous liquids is further tested by studying a model of SiO2, a glass former well known for its Arrhenius temperature behavior (strong). The method predicts an Arrhenius temperature variation, in agreement with experiments, the origin of which is revealed by both quantitative and qualitative results on transition state pathways, activation barrier analysis, energy landscape connectivity, and atomistic activation mechanisms. Also predicted is a transition from fragile to strong behavior at a lower viscosity, below the range of measurements, which had been previously suggested on the basis of molecular dynamics simulations. By systematically comparing our findings with corresponding results on the binary Lennard-Jones system (fragile) we gain new insights into the topographical features of the potential energy landscape, characteristics that distinguish strong from fragile glassy systems. We interpret fragility as a universal manifestation of slowing of dynamics when the system becomes trapped in deep energy basins. As a consequence, all glass-forming systems, when cooled from their normal liquid state, should exhibit two transitions in temperature scaling of the viscosity, a strong-to-fragile crossover followed by a second transition reverting back to strong behavior. (C) 2009 American Institute of Physics. [doi:10.1063/1.3243854]
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