Evidence of a fractional Debye-Stokes-Einstein law in supercooled o-terphenyl

Andreozzi, Laura; Schino, Andrea Di; Giordano, Marco; Leporini, Dino

doi:10.1209/epl/i1997-00301-2

Cited by 90 publications

(143 citation statements)

References 26 publications

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“…* The lineshapes in Fig. 2 are strikingly similar to the usual ones of spin probes dissolved in viscous liquids (14,31,33,(36)(37)(38). At low temperatures (Յ90 K) the ESR lineshape exhibits the rigid-limit pattern, namely the reorientation of TEMPOL is very slow (rotational correlation time Ռ max Ϸ 0.1 s).…”

Section: Resultssupporting

confidence: 57%

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ESR evidence for 2 coexisting liquid phases in deeply supercooled bulk water

Banerjee

Bhat

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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Using electron spin resonance spectroscopy (ESR), we measure the rotational mobility of probe molecules highly diluted in deeply supercooled bulk water and negligibly constrained by the possible ice fraction. The mobility increases above the putative glass transition temperature of water, T g ‫؍‬ 136 K, and smoothly connects to the thermodynamically stable region by traversing the so called ''no man's land'' (the range 150 -235 K), where it is believed that the homogeneous nucleation of ice suppresses the liquid water. Two coexisting fractions of the probe molecules are evidenced. The 2 fractions exhibit different mobility and fragility; the slower one is thermally activated (low fragility) and is larger at low temperatures below a fragile-to-strong dynamic cross-over at Ϸ225 K. The reorientation of the probe molecules decouples from the viscosity below decoupling of transport properties ͉ dynamic cross-over in water ͉ dynamic heterogeneity ͉ supercooled water ͉ polycrystalline materials T he physical properties of water are far from being completely understood. Several thermodynamic and dynamic anomalies are known or anticipated in the metastable supercooled regime that influence the equilibrium states and have deep impact in biology, astrophysics, glaciology, and atmospheric science (1-3). At ambient pressure, the supercooled regime ranges between the commonly accepted value of the glass transition temperature T g ϭ 136 K and the freezing temperature T m ϭ 273.15 K. Above T g , amorphous water transforms into a highly viscous fluid (4, 5). Crystallization into metastable cubic ice (I c ) at T X Ϸ 150 K with further transformation to the usual hexagonal form of ice I h is reported (1, 6). On the other hand, bulk water at atmospheric pressure can be supercooled below its melting temperature down to the homogeneous nucleation temperature T H Ϸ 235 K, below which it usually crystallizes to I h . Thus, the region between T X and T H is often regarded as a region where liquid water cannot be observed [''no man's land,'' NML (1)]. Nonetheless, the coexistence of crystals and deeply supercooled liquids was suspected almost 1 century ago for bulk systems (7). More recently, evidence that water and cubic ice coexist in thin films in the temperature range 140-210 K was reported (8-11). The existence of liquid water has been also shown experimentally in veins (or so-called triple junctions) of polycrystalline ice (12) that serve as interfacial reservoirs for impurities (13-15). The size of such reservoirs is thermodynamically defined by surface forces and also by the curvature of the surface (i.e., the Kelvin effect in veins) (11, 16). In pure ice, the reservoir size increases when approaching the melting point (17). Notably, recent simulations concluded that in polycrystalline materials grain boundaries exhibit the dynamics of glass-forming liquids (45).This background motivated us to investigate the coexistence of ice and supercooled water in large volumes in an attempt to characterize the dynamical properties of the li...

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Section: Resultssupporting

confidence: 57%

“…Both the FSC and DH in supercooled water drive the breakdown of the SE and DSE relations (18,(26)(27)(28). The DSE breakdown was already observed by ESR in supercooled liquids (31). We evaluated the DSE ratio R DSE ϵ /( f T) (to be constant according to the DSE law).…”

Section: Resultsmentioning

confidence: 99%

ESR evidence for 2 coexisting liquid phases in deeply supercooled bulk water

Banerjee

Bhat

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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“…5,6 This complex dynamics breaks down familiar laws like the Stokes-Einstein (SE) (Refs. [5][6][7][8][9] and Debye-Stokes-Einstein [8][9][10][11][12][13][14][15] laws that account for the coupling of the shear viscosity η with the translational and the rotational diffusion, respectively. Here, we focus on the SE law which for a sphere with radius a and stick boundary conditions reads…”

Section: Introductionmentioning

confidence: 99%

Communication: Fast and local predictors of the violation of the Stokes-Einstein law in polymers and supercooled liquids

Puosi

Leporini

2012

The Journal of Chemical Physics

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The violation of the Stokes-Einstein (SE) law is investigated in a melt of linear chains by extensive molecular-dynamics simulations. It is found that the SE breakdown is signaled (with 5% uncertainty) by the monomer mean-square displacement u 2 on the picosecond time scale. On this time scale the displacements of the next-next-nearest neighbors are uncorrelated. It is shown that: (i) the SE breakdown occurs when u 2 is smaller than the breadth of the distribution of the square displacements to escape from the first-neighbors cage, (ii) the dynamical heterogeneity affects the form of the master curve of the universal scaling between the structural relaxation and u 2 .

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“…* Electronic address: bbagchi@sscu.iisc.ernet.in; URL: http://sscu.iisc.ernet.in/prg/faculty/biman_bagchi.htm In many cases, the ratio τ 1 /τ 2 is found to fall below three. In particular, in supercooled liquids, the ratio is known to approach unity at low temperatures and related issues (like translation-rotation decoupling) that have given rise to considerable amount of discussion [6,7,8,9,10,11,12,13,14,15,16,17]. One often invokes the breakdown of Debye diffusion model, which requires small angle Brownian rotational motion for its validity, due to the emergence of large scale hopping involving large angular jumps.…”

Section: Introductionmentioning

confidence: 99%

Complete breakdown of the Debye model of rotational relaxation near the isotropic-nematic phase boundary: Effects of intermolecular correlations in orientational dynamics

2006

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The Debye-Stokes-Einstein (DSE) model of rotational diffusion predicts that the rotational correlation times τ l vary as [l(l + 1)] −1 , where l is the rank of the orientational correlation function (given in terms of the Legendre polynomial of rank l). One often finds significant deviation from this prediction, in either direction. In supercooled molecular liquids where the ratio τ1/τ2 falls considerably below three (the Debye limit), one usually invokes a jump diffusion model to explain the approach of the ratio τ1/τ2 to unity. Here we show in a computer simulation study of a standard model system for thermotropic liquid crystals that this ratio becomes much less than unity as the isotropic-nematic phase boundary is approached from the isotropic side. Simultaneously, the ratio τ2/η (where η is the shear viscosity of the liquid) becomes much larger than hydrodynamic value near the I-N transition. We have also analyzed the break down of the Debye model of rotational diffusion in ratios of higher order rotational correlation times. We show that the break down of the DSE model is due to the growth of orientational pair correlation and provide a mode coupling theory analysis to explain the results.

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Evidence of a fractional Debye-Stokes-Einstein law in supercooled o-terphenyl

Cited by 90 publications

References 26 publications

ESR evidence for 2 coexisting liquid phases in deeply supercooled bulk water

ESR evidence for 2 coexisting liquid phases in deeply supercooled bulk water

Communication: Fast and local predictors of the violation of the Stokes-Einstein law in polymers and supercooled liquids

Complete breakdown of the Debye model of rotational relaxation near the isotropic-nematic phase boundary: Effects of intermolecular correlations in orientational dynamics

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