CiteULike: dchen's Tanaka

Two-order-parameter model of the liquid-glass transition. III. Universal patterns of relaxations in glass-forming liquids

Hajime Tanaka — 2008-05-13T17:22:55-00:00

Journal of Non-Crystalline Solids, Vol. 351, No. 43-45. (1 November 2005), pp. 3396-3413.

In the preceding companion papers (paper I and II), we propose a possible origin of the slow dynamics associated with the liquid-glass transition in the light of our two-order-parameter model of liquids. Our model suggests that there exist two levels of dynamic structural heterogeneity, namely, [`]locally favored structures and their clusters' and [`]metastable solid-like islands'. On the basis of this picture, we consider how all the dynamic modes associated with a glass transition, covering from the boson peak to the structural relaxation ([alpha]) mode, can be explained within the same model. We assign the boson peak to (quasi-) localized vibrational modes characteristic of locally favored structures and their clusters and the ultrafast mode to their overdamped states. We assign the fast [beta] mode to the restricted [`]translational' motion, while the slow [beta] mode to the restricted [`]rotational' (librational) motion characteristic of molecules in metastable islands, which exist only below . The [alpha] mode is associated with dynamics of creation and annihilation of metastable islands below . The appearance and disappearance of the modes as a function of the temperature are discussed, focusing on the behavior of locally favored structures and metastable solid-like islands.

Relationship among glass-forming ability, fragility, and short-range bond ordering of liquids

Hajime Tanaka — 2008-05-13T15:47:46-00:00

Journal of Non-Crystalline Solids, Vol. 351, No. 8-9. (1 April 2005), pp. 678-690.

Glass-forming ability characterizes how easily we can avoid crystallization and thus make a glassy state of material from its liquid state upon cooling. Its quantitative measure is given by the critical cooling rate, which is the minimum cooling rate required for the formation of glass, or the avoidance of crystal nucleation. Here we consider what physical factors control the glass-forming ability of a liquid. We argue that short-range bond ordering, which is induced by a symmetry-selective part of the interaction potential, causes frustration against crystallization and helps vitrification if its local symmetry is not consistent with that of the equilibrium crystal. Based on this physical picture, we propose that the degree of short-range bond ordering in a liquid should be a new additional physical factor controlling the glass-forming ability. According to our model, it is also a controlling factor of the fragility, which characterizes how steeply viscosity increases upon cooling. This picture suggests a negative correlation between the glass-forming ability and the fragility. The close relationship between the glass-forming ability and the quasicrystal-forming ability in metallic glass formers is also discussed in the light of our model.

Kinetics of ergodic-to-nonergodic transitions in charged colloidal suspensions: Aging and gelation

Hajime Tanaka — 2008-05-13T15:20:47-00:00

Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 71, No. 2. (2005)

There are two types of isotropic disordered nonergodic states in colloidal suspensions: colloidal glasses and gels. In a recent paper [H. Tanaka, J. Meunier, and D. Bonn, Phys. Rev. E 69, 031404 (2004)], we discussed the static aspect of the differences and the similarities between the two. In this paper, we focus on the dynamic aspect. The kinetics of the liquid-glass transition is called "aging," while that of the sol-gel transition is called "gelation." The former is primarily governed by repulsive interactions between particles, while the latter is dominated by attractive interactions. Slowing down of the dynamics during aging reflects the increasing cooperativity required for the escape of a particle from the cage formed by the surrounding particles, while that during gelation reflects the increase in the size of particle clusters towards the percolation transition. Despite these clear differences in the origin of the slowing down of the kinetics between the two, it is not straightforward experimentally to distinguish them in a clear manner. For an understanding of the universal nature of ergodic-to-nonergodic transitions, it is of fundamental importance to elucidate the differences and the similarities in the kinetics between aging and gelation. We consider this problem, taking Laponite suspension as an explicit example. In particular, we focus on the two types of nonergodic states: (i) an attractive gel formed by van der Waals attractions for high ionic strengths and (ii) a repulsive Wigner glass stabilized by long-range Coulomb repulsions for low ionic strengths. We demonstrate that the aging of colloidal Wigner glass crucially differs not only from gelation, but also from the aging of structural and spin glasses. The aging of the colloidal Wigner glass is characterized by the unique cage-forming regime that does not exist in the aging of spin and structural glasses.

Colloidal Aggregation in a Nematic Liquid Crystal: Topological Arrest of Particles by a Single-Stroke Disclination Line

Takeaki Araki — 2008-05-13T00:24:02-00:00

Physical Review Letters, Vol. 97, No. 12. (2006)

We numerically study many-body interactions among colloidal particles suspended in a nematic liquid crystal, using a fluid particle dynamics method, which properly incorporates dynamical coupling among particles, nematic orientation, and flow field. Based on simulation results, we propose a new type of interparticle interaction in addition to well-known quadrupolar interaction for particles accompanying Saturn-ring defects. This interaction is mediated by the defect of the nematic phase: upon nematic ordering, a closed disclination loop binds more than two particles to form a sheetlike dynamically arrested structure. The interaction depends upon the topology of a disclination loop binding particles, which is determined by aggregation history.

Control of the Liquid-Liquid Transition in a Molecular Liquid by Spatial Confinement

Rei Kurita — 2007-11-28T18:24:35-00:00

Physical Review Letters, Vol. 98, No. 23. (2007)

Generally, phase transitions are seriously affected by spatial confinement. This effect is important for its own sake, but also for applications to nanotechnology. Here we report the first systematic experimental study on confinement effects on a liquid-liquid transition of a molecular liquid. We found that one liquid can be transformed into another purely by spatial confinement. This indicates that the liquid state cannot be specified by the temperature and pressure alone, but it is also affected by its size in a discontinuous manner: the phase of a liquid in a narrow space can, in principle, be different from that in the bulk. This finding would deepen our basic understanding of the liquid state.

Laponite: Aging and Shear Rejuvenation of a Colloidal Glass

Daniel Bonn — 2008-04-25T23:08:28-00:00

Physical Review Letters, Vol. 89, No. 1. (13 June 2002), 015701.

A simple physical model of liquid - glass transition: intrinsic fluctuating interactions and random fields hidden in glass-forming liquids

Hajime Tanaka — 2008-03-04T20:48:17-00:00

Journal of Physics: Condensed Matter, Vol. 10, No. 14. (1998), pp. L207-L214.

We propose that glass-forming liquids are intrinsically under the influences of both fluctuating interactions and random fields well-known in the field of spin systems. This is due to the frustration between the isotropic and anisotropic parts of effective intermolecular interactions. Our model indicates the existence of two key temperatures relevant to the glass transition, the density ordering point and the Vogel - Fulcher temperature . Between and , a system has features similar to the `Griffiths phase', while below it has those peculiar to the `spin-glass phase'. This picture naturally and universally explains vitrification behaviour from its strong to its fragile limit.

Two-order-parameter description of liquids. I. A general model of glass transition covering its strong to fragile limit

Hajime Tanaka — 2008-03-01T22:29:10-00:00

The Journal of Chemical Physics, Vol. 111, No. 7. (1999), pp. 3163-3174.

Two-order-parameter model of the liquid-glass transition. II. Structural relaxation and dynamic heterogeneity

Hajime Tanaka — 2008-03-01T21:35:15-00:00

Journal of Non-Crystalline Solids, Vol. 351, No. 43-45. (1 November 2005), pp. 3385-3395.

We propose that there exist two key temperatures relevant to glass transition: (i) a transition from the ordinary-liquid to the frustrated metastable-liquid (the Griffiths-phase-like) state at , which is characterized by the appearance of metastable high-density solid-like islands and the resulting appearance of the cooperative nature of [alpha] relaxation, and (ii) another transition into the spin-glass-like state and the resulting divergence of the [alpha] relaxation time at T0. is a density-ordering (melting) point of the corresponding hypothetical pure system that is free from disorder effects. Below , a system has a complex free-energy landscape characteristic of the frustrated metastable-liquid state; metastable solid-like islands with different densities coexist and fluctuate dynamically. In our model, the [alpha] mode is associated with dynamics of creation and annihilation of metastable islands below . The metastable solid-like islands are the origin of dynamic heterogeneity. We propose a modified Vogel-Fulcher law, which can phenomenologically describe the Arrhenius/Vogel-Fulcher crossover induced by a transition from the ordinary-liquid to the frustrated metastable-liquid state around . We also argue that the hidden crystalline ordering in metastable islands may cause the change in the structure factor of a supercooled liquid below , which is more enhanced upon cooling.

Two-order-parameter model of the liquid-glass transition. I. Relation between glass transition and crystallization

Hajime Tanaka — 2008-03-01T20:17:52-00:00

Journal of Non-Crystalline Solids, Vol. 351, No. 43-45. (1 November 2005), pp. 3371-3384.

Recently we proposed a two-order-parameter model of liquid to understand the liquid-glass transition, liquid-liquid transition, and anomalies of water-type liquids in a unified manner. Here we discuss the relation between our model and previous models of the liquid-glass transition, focusing on the difference in the basic standpoint among the models. We argue that (i) actual liquids universally have a tendency of spontaneous formation of locally favored structures and (ii) liquid-glass transition is controlled by the competition between long-range density ordering toward crystallization and short-range bond ordering toward the formation of locally favored structures due to the incompatibility in their symmetry. Thus, we regard vitrification as phenomena that are intrinsically related to crystallization. Previous models, on the other hand, regard vitrification as a result of (a) an homogeneous increase in the density and the resulting cooperativity in molecular motion or (b) the frustration intrinsic to a liquid state itself. Accordingly, they presuppose the kinetic avoidance of crystallization and thus do not put focus on `crystallization'. This leads to the essential difference in the physical picture between our model and previous models. By comparing models, we aim at gaining further insight into what is the physical origin of the liquid-glass transition and its possible connection with crystallization.