Temperature dependences of viscosity of glass-forming substances at constant fictive temperatures

Mazurin, O. V.; Startsev, Yu. K.; Stoljar, S.V.

doi:10.1016/0022-3093(82)90284-8

Cited by 44 publications

(23 citation statements)

References 2 publications

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“…Fig. 3B shows that the current model produces the narrowest distribution of ϱ values, in agreement with arguments concerning the universality of the ϱ parameter for a given class of materials (33)(34)(35), viz., in the limit of infinite temperature, the details of the interatomic potentials are no longer important because the system is dominated by kinetic energy. We note that this argument for a universal ϱ implicitly assumes simple exponential relaxation in the high-temperature limit (36).…”

Section: Resultssupporting

confidence: 70%

Viscosity of glass-forming liquids

Mauro

Yue

Ellison

et al. 2009

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

821

806

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The low-temperature dynamics of ultraviscous liquids hold the key to understanding the nature of glass transition and relaxation phenomena, including the potential existence of an ideal thermodynamic glass transition. Unfortunately, existing viscosity models, such as the Vogel-Fulcher-Tammann (VFT) and Avramov-Milchev (AM) equations, exhibit systematic error when extrapolating to low temperatures. We present a model offering an improved description of the viscosity-temperature relationship for both inorganic and organic liquids using the same number of parameters as VFT and AM. The model has a clear physical foundation based on the temperature dependence of configurational entropy, and it offers an accurate prediction of low-temperature isokoms without any singularity at finite temperature. Our results cast doubt on the existence of a Kauzmann entropy catastrophe and associated ideal glass transition.modeling ͉ supercooled liquids ͉ configurational entropy ͉ relaxation P erhaps the most intriguing feature of a supercooled liquid is its dramatic rise in viscosity as it is cooled toward the glass transition. This sharp, super-Arrhenius increase is accompanied by very little change in the structural features observable by typical diffraction experiments. Several basic questions remain unanswered:1. Is the behavior universal (i.e., is the viscosity of all liquids described by the same underlying model)?2. Does the viscosity diverge at some finite temperature below the glass transition (i.e., is there a dynamic singularity)?3. Is the existence of a thermodynamic singularity the cause of the dramatic viscous slowdown?Answers to these questions are critical for understanding the behavior of deeply supercooled liquids. Unfortunately, equilibriumviscosity measurements cannot be carried out at temperatures much below the glass transition owing to the long structural relaxation time. It thus becomes critical to find a model that best describes the temperature dependence of viscosity by using the fewest possible number of fitting parameters (1, 2). Because two parameters are needed for a simple Arrhenius description, modeling of super-Arrhenius behavior requires a minimum of three parameters. We focus on three-parameter models only, with the goal of describing the universal physics of supercooled liquid viscosity in the most economical form possible.The most popular viscosity model is the Vogel-FulcherTammann (VFT) equation (3) log 10 ͑T, x͒ ϭ log 10 ϱ ͑x͒ ϩ A͑x͒where T is temperature, x is composition, and the three VFT parameters ( ϱ , A, and T 0 ) are obtained by fitting Eq. 1 to experimentally measured viscosity data. In the polymer science community, Eq. 1 is also known as the Williams-Landel-Ferry (WLF) equation (4). Although VFT has met with notable success for a variety of liquids, there is some indication that it breaks down at low temperatures (3, 5). Another successful three-parameter viscosity model is the Avramov-Milchev (AM) equation (6), derived based on an atomic hopping approach:where ϱ , , and ␣ are fittin...

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Section: Resultssupporting

confidence: 70%

Viscosity of glass-forming liquids

Mauro

Yue

Ellison

et al. 2009

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

821

806

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show abstract

“…Furthermore, the slope should depend on the depth of previous annealing. Data generally supporting this expectation were obtained long ago by Russian workers making very sensitive viscosity measurements on silicate glasses 159 and are qualitatively confirmed by recent measurements of dielectric relaxation on polymers well below T g 160 ͓see Fig. 21͑a͔͒.…”

Section: B19 Shear Relaxation Versus Bulksupporting

confidence: 71%

“…Such have been described for viscous relaxation by Mazurin et al 159 and for response to torsional stresses by McKenna et al ͑Refs. 128 or 136͒.…”

Section: B22 Value Of the Stretching Exponent In Constant Structurmentioning

confidence: 99%

Relaxation in glassforming liquids and amorphous solids

Angell

Ngai

McKenna

et al. 2000

Journal of Applied Physics

2,108

1,876

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The field of viscousliquid and glassysolid dynamics is reviewed by a process of posing the key questions that need to be answered, and then providing the best answers available to the authors and their advisors at this time. The subject is divided into four parts, three of them dealing with behavior in different domains of temperature with respect to the glass transition temperature, Tg,and a fourth dealing with "short time processes. " The first part tackles the high temperature regime T>Tg, in which the system is ergodic and the evolution of the viscousliquid toward the condition at Tg is in focus. The second part deals with the regime T∼Tg, where the system is nonergodic except for very long annealing times, hence has time-dependent properties (aging and annealing). The third part discusses behavior when the system is completely frozen with respect to the primary relaxation process but in which secondary processes, particularly those responsible for "superionic" conductivity, and dopart mobility in amorphous silicon, remain active. In the fourth part we focus on the behavior of the system at the crossover between the low frequency vibrational components of the molecular motion and its high frequency relaxational components, paying particular attention to very recent developments in the short time dielectric response and the high Qmechanical response. The field of viscous liquid and glassy solid dynamics is reviewed by a process of posing the key questions that need to be answered, and then providing the best answers available to the authors and their advisors at this time. The subject is divided into four parts, three of them dealing with behavior in different domains of temperature with respect to the glass transition temperature, T g , and a fourth dealing with ''short time processes.'' The first part tackles the high temperature regime TϾT g , in which the system is ergodic and the evolution of the viscous liquid toward the condition at T g is in focus. The second part deals with the regime TϳT g , where the system is nonergodic except for very long annealing times, hence has time-dependent properties ͑aging and annealing͒. The third part discusses behavior when the system is completely frozen with respect to the primary relaxation process but in which secondary processes, particularly those responsible for ''superionic'' conductivity, and dopart mobility in amorphous silicon, remain active. In the fourth part we focus on the behavior of the system at the crossover between the low frequency vibrational components of the molecular motion and its high frequency relaxational components, paying particular attention to very recent developments in the short time dielectric response and the high Q mechanical response.

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“…Below a fictive temperature, T f [25], the non-equilibrium glass structure is frozen, simultaneously, the viscosity decouples from the equilibrium viscosity curve and the logarithmic viscosity increases linearly with 1/T. This decoupled viscosity is called the iso-structural viscosity g iso [22,23]. The activation energy for the linear change of g iso with 1/T is referred to as the activation energy for iso-structural flow, E iso , which can be derived from Eq.…”

Section: Tablementioning

confidence: 99%

“…The present paper will focus on the study of oxide liquids. This paper uses the concept of the iso-structural viscosity [22,23] to explore the origin of the of the liquid fragility, and to derive S c functions from the AM and VFT equations. The ratio between the activation energy for the equilibrium viscosity and that for the iso-structural viscosity will be derived from the mentioned four equations and quantitatively determined by fitting the viscosity data to those equations.…”

Section: Introductionmentioning

confidence: 99%

The iso-structural viscosity, configurational entropy and fragility of oxide liquids

Yue

2009

Journal of Non-Crystalline Solids

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Temperature dependences of viscosity of glass-forming substances at constant fictive temperatures

Cited by 44 publications

References 2 publications

Viscosity of glass-forming liquids

Viscosity of glass-forming liquids

Relaxation in glassforming liquids and amorphous solids

The iso-structural viscosity, configurational entropy and fragility of oxide liquids

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