Intermolecular Forces and the Glass Transition
Document Type
Article
Source
The Journal of Physical Chemistry
ISSN
0022-3654
Volume
112
Issue
2
First Page
301
Last Page
312
Publication Date
2008
Department
Natural Sciences and Mathematics
Abstract
Random first-order transition theory is used to determine the role of attractive and repulsive interactions in the dynamics of supercooled liquids. Self-consistent phonon theory, an approximate mean field treatment consistent with random first-order transition theory, is used to treat individual glassy configurations, whereas the liquid phase is treated using common liquid-state approximations. Free energies are calculated using liquid-state perturbation theory. The transition temperature,, the temperature where the onset of activated behavior is predicted by mean field theory; the lower crossover temperature,, where barrierless motions actually occur through fractal or stringy motions (corresponding to the phenomenological mode coupling transition temperature); and, the Kauzmann temperature (corresponding to an extrapolated entropy crisis), are calculated in addition to, the glass transition temperature that corresponds to laboratory cooling rates. Relationships between these quantities agree well with existing experimental and simulation data on van der Waals liquids. Both the isobaric and isochoric behavior in the supercooled regime are studied, providing results for ΔCV and ΔCp that can be used to calculate the fragility as a function of density and pressure, respectively. The predicted variations in the α-relaxation time with temperature and density conform to the empirical density−temperature scaling relations found by Casalini and Roland. We thereby demonstrate the microscopic origin of their observations. Finally, the relationship first suggested by Sastry between the spinodal temperature and the Kauzmann temperatures, as a function of density, is examined. The present microscopic calculations support the existence of an intersection of these two temperatures at sufficiently low temperatures.
Rights
Copyright © 2008 American Chemical Society. All rights reserved.
PubMed ID
17990867