Fragile strong liquids: A saddles-ruled scenario
Department of Physics and Astronomy, The University
Oxford Road, M13 9PL, Manchester, UK
Accepted: 1 December 2000
In the context of the energy landscape description of supercooled liquids, we propose an explanation for the different behaviour of fragile and strong liquids. Above Goldstein's temperature Tx, diffusion is interpreted as a motion in the phase space among saddles of the potential energy. Two mechanisms of diffusion then arise: mechanism A takes place when the system overcomes potential-energy barriers along stable uphill directions, while mechanism B consists in finding unstable downhill directions out of a saddle. Depending on the mutual efficiency of A and B, the usual classification of liquids in fragile and strong is recovered. Moreover, this scenario naturally predicts the possibility of a fragile-to-strong crossover when lowering the temperature.
PACS: 61.20.Gy – Theory and models of liquid structure / 64.70.Pf – Glass transitions
© EDP Sciences, 2001