28 research outputs found
Landscape equivalent of the shoving model
It is shown that the shoving model expression for the average relaxation time
of viscous liquids follows largely from a classical "landscape" estimation of
barrier heights from curvature at energy minima. The activation energy involves
both instantaneous bulk and shear moduli, but the bulk modulus contributes less
than 8% to the temperature dependence of the activation energy. This reflects
the fact that the physics of the two models are closely related.Comment: 4 page
The kinetic fragility of liquids as manifestation of the elastic softening
We show that the fragility , the steepness of the viscosity and relaxation
time close to the vitrification, increases with the degree of elastic
softening, i.e. the decrease of the elastic modulus with increasing
temperature, in universal way. This provides a novel connection between the
thermodynamics, via the modulus, and the kinetics. The finding is evidenced by
numerical simulations and comparison with the experimental data of glassformers
with widely different fragilities (), leading to a
fragility-independent elastic master curve extending over eighteen decades in
viscosity and relaxation time. The master curve is accounted for by a cavity
model pointing out the roles of both the available free volume and the cage
softness. A major implication of our findings is that ultraslow relaxations,
hardly characterised experimentally, become predictable by linear elasticity.
As an example, the viscosity of supercooled silica is derived over about
fifteen decades with no adjustable parameters.Comment: 7 pages, 6 figures; Added new results, improved the theoretical
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A bipartite system for the constitutive and inducible expression of high levels of foreign proteins in plants
Elevated stromal Foxp3+ regulatory T cells combined with low density CD8+ cytotoxic T cells are associated with colorectal metastatic tumour progression
Observations and Numerical Simulations of Urban Heat Island and Sea Breeze Circulations over New York City
On the role of basic residues of head-to-tail cyclic bradykinin analogues on rat duodenum relaxation
Quantum effects in dynamics of water and other liquids of light molecules
Nuclear quantum effects in atomic motions are well known at low temperatures K. Recent studies, however, suggested that nuclear quantum effects in systems of light molecules (e.g., water) might play an important role in structural dynamics and provide non-negligible contributions at such temperatures, and even up to ambient temperature. In this article, we discuss experimental evidences of the quantum effects in glass transition in liquids of light molecules and possible theoretical descriptions of these effects. We show that quantum effects may qualitatively change the temperature behavior of the structural relaxation time in supercooled liquids leading to deviations of some well-established properties of the glass transition when it happens at low temperatures. We also demonstrate that unusual behavior of water dynamics at low temperatures, including apparent fragile-to-strong crossover, can be ascribed to nuclear quantum effects