Probing a Critical Length-Scale at the Glass Transition

Upon cooling, dense liquids may stop flowing without arranging in a coherent, ordered crystal structure. Molecular motion becomes spectacularly slow and the result is a glass, a microscopically disordered solid with mechanical, electrical or optical properties very different from the crystal.

More than 50 years of scientific debate could not clarify whether glasses are a thermodynamic state of matter or merely slow liquids. We here tackle this fundamental question from a fresh perspective which is inspired by a modern approach to nonequilibrium thermodynamics.

From newly designed computer simulations, we have found the first direct evidence that the slowing down indeed originates from a change in the underlying structure as dramatic as observed in phase transitions between different states of matter.

Original Abstract

Majid Mosayebi, Emanuela Del Gado, Patrick Ilg, and Hans Christian Öttinger
Polymer Physics, ETH Zürich, Department of Materials, CH-8093 Zürich, Switzerland

Received 30 March 2010; published 21 May 2010

We give evidence of a clear structural signature of the glass transition, in terms of a static correlation length with the same dependence on the system size, which is typical of critical phenomena. Our approach is to introduce an external, static perturbation to extract the structural information from the system’s response. In particular, we consider the transformation behavior of the local minima of the underlying potential energy landscape (inherent structures), under a static deformation. The finite-size scaling analysis of our numerical results indicate that the correlation length diverges at a temperature T_c, below the temperatures where the system can be equilibrated. Our numerical results are consistent with random first order theory, which predicts such a divergence with a critical exponent ν=2/3 at the Kauzmann temperature, where the extrapolated configurational entropy vanishes.

© 2010 The American Physical Society

URL: http://link.aps.org/doi/10.1103/PhysRevLett.104.205704

DOI: 10.1103/PhysRevLett.104.205704

PACS: 64.70.Q-, 05.20.Jj, 61.43.Fs