Karmakar, Smarajit and Dasguptaa, Chandan and Sastry, Srikanth (2009) Growing length and time scales in glass-forming liquids. In: Proceedings Of The National Academy Of Sciences Of The United States Of America, 106 (10). pp. 3675-3679.
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The glass transition, whereby liquids transform into amorphous solids at low temperatures, is a subject of intense research despite decades of investigation. Explaining the enormous increase in relaxation times of a liquid upon supercooling is essential for understanding the glass transition. Although many theories, such as the Adam-Gibbs theory, have sought to relate growing relaxation times to length scales associated with spatial correlations in liquid structure or motion of molecules, the role of length scales in glassy dynamics is not well established. Recent studies of spatially correlated rearrangements of molecules leading to structural relaxation, termed ``spatially heterogeneous dynamics,'' provide fresh impetus in this direction. A powerful approach to extract length scales in critical phenomena is finite-size scaling, wherein a system is studied for sizes traversing the length scales of interest. We perform finite-size scaling for a realistic glass-former, using computer simulations, to evaluate the length scale associated with spatially heterogeneous dynamics, which grows as temperature decreases. However, relaxation times that also grow with decreasing temperature do not exhibit standard finite-size scaling with this length. We show that relaxation times are instead determined, for all studied system sizes and temperatures, by configurational entropy, in accordance with the Adam-Gibbs relation, but in disagreement with theoretical expectations based on spin-glass models that configurational entropy is not relevant at temperatures substantially above the critical temperature of mode-coupling theory. Our results provide new insights into the dynamics of glass-forming liquids and pose serious challenges to existing theoretical descriptions.
|Item Type:||Journal Article|
|Additional Information:||Copyright of this article belongs to National Academy of Sciences.|
|Keywords:||correlation length;dynamic heterogeneity;finite-size scaling;glass transition;relaxation time.|
|Department/Centre:||Division of Physical & Mathematical Sciences > Physics|
|Date Deposited:||23 Jul 2009 07:05|
|Last Modified:||19 Sep 2010 05:29|
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