Microscopic dynamics of glycerol in its crystalline and glassy states

Bermejo, F. J.; Criado, A.; Andrés, A. de; Enciso, E.; Schober, H.

doi:10.1103/physrevb.53.5259

Cited by 51 publications

(39 citation statements)

References 35 publications

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“…The storage moduli obtained from oscillatory measurements are centered around 2.2 ( 0.5 GPa, which is consistent with previous measurements. 7 A subsequent strain sweep at f ) 0.1 Hz at a normal force F N ) 20 N shows that the storage modulus is constant over a range of strain amplitudes, although for larger strain the elastic modulus decreases while the loss modulus increases. This is either due to slip or shearinduced rejuvenation of the solid.…”

Section: Resultsmentioning

confidence: 96%

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Aging and Solidification of Supercooled Glycerol

et al. 2010

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We experimentally investigate the solidification of supercooled glycerol during aging that has recently been observed by Zondervan et al. We find that a slow cooling at 5 K/h prior to the aging is required for solidification to take place. Furthermore, we show that the time of onset depends strongly on the aging temperature which we varied between 220 and 240 K. The nature of the solid phase remains unclear. The experiments show that upon heating the solid glycerol melts at the crystal melting point. However, rheology experiments in the plate-plate geometry revealed the growth of a soft, slushlike phase that is distinct from a crystal grown by seeding at the same aging temperature. The slushlike glycerol grows from a nucleation point at almost the same speed as a seeded crystal quenched to the same temperature, but its shear modulus is almost 2 orders of magnitude lower than the crystal phase, which we measure independently. While solidification was reproducible in the Couette geometry, it was not in the plate-plate geometry.

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Section: Resultsmentioning

confidence: 96%

“…7 Since the control measurements on frozen water have pointed out the compliance issue, the plateau values of the moduli of the aged glycerol we measured in the Couette geometry cannot be trusted.…”

Section: Resultsmentioning

confidence: 96%

Aging and Solidification of Supercooled Glycerol

et al. 2010

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“…low-frequency Raman spectra ͑below some 20 meV͒ and the coincidence of the position of the intense Bragg reflection with the maximum of S(Q) in the canonical glass pinpoints the existence of remarkable correlations between molecular orientations as it is known to occur in the glass phase of other alcohols. 9,12 The Raman spectra of the glass and SPC solid show rather similar shapes of the frequency distributions. Because of the isotropy of the glass and the orientational disorder in the SPC, the Raman intensities could be considered to be directly related to the vibrational density of states through the usual expression Z R ()ϰI()/͓n()ϩ1͔, where in the absence of additional information a quadratic frequency dependence for the C() light-to-vibration coupling function is assumed ͑i.e., complete randomness of couplings͒.…”

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confidence: 89%

Evidence for a supercooled plastic-crystal phase in solid ethanol

et al. 1996

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The existence of an orientationally disordered cubic phase of solid ethanol is revealed by x-ray diffraction and Raman spectroscopic measurements. Such a phase, whose existence was postulated some time ago on the basis of specific-heat measurements, is produced by quenching below some 95 K a plastic crystal formed upon melting and subsequent annealing of the topologically disordered ͑glassy͒ solid. The relevance of the present findings for current discussions on glassy dynamics is analyzed in some detail.Despite recent advances in our understanding of the microscopic mechanisms driving the dynamics of glasses at intermediate ͑above 1 K͒ temperatures, 1 most studies regarding topologically disordered solids ͑i.e., real glassy materials͒ still encounter substantial difficulties when trying to go beyond descriptions of the data by means of phenomenological approaches. This contrasts with a more developed understanding regarding the dynamics of disordered crystals formed by either mixed 2 or chemically homogeneous ͑plastic and glassy crystals 3,4 ͒ materials, which in common with structural glasses exhibit some features considered as fingerprints of the glassy dynamics. Such developments are, however, restricted to materials which being disordered in some quantity ͑chemical composition, relative molecular orientations, etc.͒ still have an underlying crystal lattice, thus enabling the calculation of a number of physical properties ͑i.e., coupling between molecular translations and rotations, softening of elastic constants due to disorder, anomalous dielectric behavior, etc.͒ in terms of well-established techniques.2 The relevance of such findings for the understanding of real glasses was not explored in detail, perhaps due to the fact that most of the existing materials can either be converted into topological or disordered-crystal states, exceptions to such a rule being rare ͑amorphous and hexagonal ice being an example which involves rather different routes of preparation which pose severe conditions when trying to compare the two in terms of transition temperatures͒.The existence of some polymorphic phase in solid ethanol which could be prepared under mild thermal conditions was known to exist since the work of Haida et al.5 who observed calorimetric anomalies distinct from those associated with the glass transition (T g ϭ97 K͒, the melting of the stable crystal (T m ϭ169 K͒, or crystallization of the supercooled liquid into such a phase (T cr Ϸ125 K͒. In fact, the presence of a well-defined exothermic anomaly at some 115 K was interpreted as the onset of a crystal phase ͑crystal II͒ which once grown exhibited a calorimetric transition into another crystalline phase ͑glassy crystal͒, showing small differences in heat capacity with those of the glass obtained by rapid cooling of the normal liquid, but evidencing a calorimetric entropy between that of the glass and the stable crystal. A NMR relaxation measurement reported later on 6 showed that the dynamics of the real glass and that of the glassy crystal as samp...

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“…Typical is a behaviour C(ω i ) ∝ ω n i with n = 1 [27] or n = 2 [28]. Also noninteger values for n [29] and a nonvanishing limit for ω i → 0 [30] have been reported.…”

Section: Distribution Of Modesmentioning

confidence: 99%

Dynamic Kerr effect responses in the terahertz range

Häberle

Diezemann

2005

The Journal of Chemical Physics

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Dynamic Kerr effect measurements provide a simple realization of a nonlinear experiment. We propose a field-off experiment where an electric field of one or several sinusoidal cycles with frequency Ω is applied to a sample in thermal equilibrium. Afterwards, the evolution of the polarizability is measured. If such an experiment is performed in the Terahertz-range it might provide valuable information about the low-frequency dynamics in disordered systems. We treat these dynamics in terms of a Brownian oscillator model and calculate the Kerr effect response. It is shown that frequency-selective behaviour can be expected. In the interesting case of underdamped vibrational motion we find that the frequency-dependence of the phonon-damping can be determined from the experiment. Also the behaviour of overdamped relaxational modes is discussed. For typical glassy materials we estimate the magnitude of all relevant quantities, which we believe to be helpful in experimental realizations.

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Microscopic dynamics of glycerol in its crystalline and glassy states

Cited by 51 publications

References 35 publications

Aging and Solidification of Supercooled Glycerol

Aging and Solidification of Supercooled Glycerol

Evidence for a supercooled plastic-crystal phase in solid ethanol

Dynamic Kerr effect responses in the terahertz range

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