Source of non-Arrhenius average relaxation time in glass-forming liquids

Dyre, Jeppe C.

doi:10.1016/s0022-3093(98)00502-x

Cited by 137 publications

(137 citation statements)

References 60 publications

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“…Actually, according to Dyre's shoving model, spherical symmetry in real flow events is probably violated, leading to some compression of surroundings and a contribution to activation energy that is proportional to bulk modulus. 45 The equivalent PEL of the shoving model also confirmed this point; thereby, activation energy must involve both shear and bulk moduli. 46 However, which of them controls the activation energy?…”

Section: B Shear-induced Dilatationmentioning

confidence: 68%

Intrinsic correlation between fragility and bulk modulus in metallic glasses

Jiang

Dai

2007

Phys. Rev. B

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A systematic study on the available data of 26 metallic glasses shows that there is an intrinsic correlation between fragility of a liquid and bulk modulus of its glass. The underlying physics can be rationalized within the formalism of potential energy landscape thermodynamics. It is surprising to find that the linear correlation between the fragility and the bulk-shear modulus ratio exists strictly at either absolute zero temperature or very high frequency. Further analyses indicate that a real flow event in bulk metallic glasses is shear dominant, and fragility is in inverse proportion to shear-induced bulk dilatation. Finally, extension of these findings to nonmetallic glasses is discussed.

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Section: B Shear-induced Dilatationmentioning

confidence: 68%

Intrinsic correlation between fragility and bulk modulus in metallic glasses

Jiang

Dai

2007

Phys. Rev. B

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“…The second aspect worth discussing is an analysis of f m in terms of a temperature-variant Arrhenius energy, which has been recently expressed by Dyre et al, 56 and Dyre 57 and in terms of what was called the ''shoving model.'' 57 They considered that molecular interactions are anharmonic near T g , with strong short-range repulsion and weak long-range attraction, and that a certain amount of energy is spent in the shoving of the surrounding molecules in a local region be-fore diffusion can occur at all.…”

Section: Temperature Dependence Of Relaxation Ratesmentioning

confidence: 99%

“…57 They considered that molecular interactions are anharmonic near T g , with strong short-range repulsion and weak long-range attraction, and that a certain amount of energy is spent in the shoving of the surrounding molecules in a local region be-fore diffusion can occur at all. This increases the volume of the aggregate from V to Vϩ⌬V.…”

Section: Temperature Dependence Of Relaxation Ratesmentioning

confidence: 99%

Effects of induced steric hindrance on the dielectric behavior and H bonding in the supercooled liquid and vitreous alcohol

Johari

Kalinovskaya

Vij

2001

The Journal of Chemical Physics

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The extent of H bonding in alcohols may be reduced by sterically hindering its OH group. This technique is used here for investigating the reasons for the prominent Debye-type dielectric relaxation observed in monohydroxy alcohols ͓Kudlik et al., Europhys. Lett. 40, 549 ͑1997͒; Hansen et al., J. Chem. Phys. 107, 1086 ͑1997͒; Kalinovskaya and Vij, ibid. 112, 3262 ͑2000͔͒, and broadband dielectric spectroscopy of supercooled liquid and glassy states of 1-phenyl-1-propanol is performed over the 165-238 K range. In its molecule, the steric hindrance from the phenyl group and the existence of optical isomers reduce the extent of intermolecular H bonding. The equilibrium permittivity data show that H-bonded chains do not form in the supercooled liquid, and the total polarization decays by three discrete relaxation processes, of which only the slower two could be resolved. The first is described by the Cole-Davidson-type distribution of relaxation times and a Vogel-Fulcher-Tammann-type temperature dependence of its average rate, which are characteristics of the ␣-relaxation process as in molecular liquids. The second is described by a Havriliak-Negami-type equation, and an Arrhenius temperature dependence, which are the characteristics of the Johari-Goldstein process of localized molecular motions. The relaxation rate's non-Arrhenius temperature dependence has been examined qualitatively in terms of the Dyre theory, which considers that the apparent Arrhenius energy itself is temperature dependent, as in the classical interpretations, and quantitatively in terms of the cooperatively rearranging region's size, without implying that there is an underlying thermodynamic transition in its equilibrium liquid. The relaxation rate also fits the power law with the critical exponent of 13.4, instead of 2-4, required by the mode-coupling theory, thereby indicating the ambiguity of the power-law equations.

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“…The shoving model assumes that the activation barrier for viscous flow has two contributions: (i) rearrangements of molecules or structural units, when a thermal fluctuation leads to extra space being created locally; (ii) "shoving" aside the surrounding liquid to reduce the first contribution. According to the shoving model, the main contribution comes from (ii), i.e., the activation energy is mainly elastic energy [5]. On a short time scale, the liquid behaves as a solid with elastic moduli equal to the instantaneous elastic moduli.…”

Section: Introductionmentioning

confidence: 99%

“…On a short time scale, the liquid behaves as a solid with elastic moduli equal to the instantaneous elastic moduli. Furthermore, it is assumed that all flow events possess spherical symmetry, i.e., the surroundings are subject to a pure shear displacement and not associated with any density change [5,51,56]. Since this displacement happens on a short time scale, the shoving work is proportional to the instantaneous shear modulus, which leads to the following expression for the relaxation time [51]:…”

Section: Introductionmentioning

confidence: 99%

Elastic interpretation of the glass transition in aluminosilicate liquids

et al. 2012

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One of the remaining puzzles of the glass transition is the origin of a glass-forming liquid's "fragility," which quantifies the departure of its relaxation time from Arrhenius activated kinetics. According to the shoving model proposed by Dyre, fragility is controlled by the instantaneous shear modulus of the liquid, since any flow event requires a local volume increase and the related activation energy is equal to the work done in shoving aside the surrounding atoms. Here, we present an in situ high-temperature Brillouin spectroscopy test of the shoving model near the glass transition of eight aluminosilicate glass-forming systems. We find that the measured viscosity data agree qualitatively with the measured temperature dependence of shear moduli, as predicted by the shoving model. However, the model systematically underpredicts the values of fragility for our aluminosilicate liquids. This suggests that the dynamics of the glass transition are governed by additional factors beyond the evolution of the shear modulus, such as configurational entropy. We have also compared the glass transition temperature T g,vis obtained from viscosity (temperature at 10 12 Pa s) with the onset temperatures of the decrease in elastic moduli (T g,elas ) and increase in the thermal expansion coefficient (T g,CTE ) during heating. While we find an approximate one-toone correlation between T g,vis and T g,CTE , it is clear that the elastic moduli probe a different frequency response of the glass structure since T g,elas is systematically lower than T g,vis .2

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Source of non-Arrhenius average relaxation time in glass-forming liquids

Cited by 137 publications

References 60 publications

Intrinsic correlation between fragility and bulk modulus in metallic glasses

Intrinsic correlation between fragility and bulk modulus in metallic glasses

Effects of induced steric hindrance on the dielectric behavior and H bonding in the supercooled liquid and vitreous alcohol

Elastic interpretation of the glass transition in aluminosilicate liquids

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