Mechanistic view of the relaxation dynamics of a simple glass-former. A bridge between the topographic and the dynamic approaches

Appignanesi, Gustavo A.; Montani, R.A.

doi:10.1016/j.jnoncrysol.2004.03.125

Cited by 9 publications

(31 citation statements)

References 20 publications

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“…As quakes are localized events in time and space, record dynamics treats aging as a strongly heterogeneous dynamical process. However, as emphasized by recent work [21][22][23][24], exponential tails in the PDF's of relevant dynamical variables also appear outside the aging regime (see also the insert of Fig. 1), i.e.…”

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confidence: 59%

Aging and intermittency in ap-spin model of a glass

Sibani¹

2006

Phys. Rev. E

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We numerically analyze the statistics of the heat flow between an aging system and its thermal bath, following a method proposed and tested for a spin-glass model in a recent paper [P. Sibani and H. J. Jensen, Europhys. Lett. 69, 563 (2005)]. The present system, which lacks quenched randomness, consists of Ising spins located on a cubic lattice, with each plaquette contributing to the total energy the product of the four spins located at its corners. Similarly to our previous findings, energy leaves the system in rare but large, so-called intermittent, bursts which are embedded in reversible and equilibriumlike fluctuations of zero average. The intermittent bursts, or quakes, dissipate the excess energy trapped in the initial state at a rate which falls off with the inverse of the age. This strongly heterogeneous dynamical picture is explained using the idea that quakes are triggered by energy fluctuations of record size, which occur independently within a number of thermalized domains. From the temperature dependence of the width of the reversible heat fluctuations we surmise that these domains have an exponential density of states. Finally, we show that the heat flow consists of a temperature independent term and a term with an Arrhenius temperature dependence. Microscopic dynamical and structural information can thus be extracted from numerical intermittency data. This type of analysis seems now within the reach of time resolved microcalorimetry techniques.

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confidence: 59%

Aging and intermittency in ap-spin model of a glass

Sibani¹

2006

Phys. Rev. E

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“…Within this realm, the discovery that glassy systems are dynamically heterogeneous represented a major breakthrough and reinforced the interest in the Adam & Gibbs heterogeneous scenario for glassy relaxation: the existence of cooperatively relaxing regions in the sample whose timescales and sizes grow as the temperature is decreased in the supercooled regime [4,5,6,7,8,9]. A complimentary and powerful framework for this field has been provided by the so-called landscape paradigm [3,10,11,12,13]: the dynamics of a glassy system can be followed as the exploration it performs of its Potential Energy Landscape (PEL), the surface generated by the potential energy of the system as a function of particle coordinates. The PEL can be partitioned into disjoint basins, where a basin is unambiguously defined as the set of points in configuration space connected to the same local minimum (called inherent structure, IS) via a steepest-descendant trajectory.…”

Section: Introductionmentioning

confidence: 99%

“…If the temperature is very low the system doesn't have enough energy to easily overcome barriers between PEL valleys, this resulting in a slowing down of the dynamics. The link between these two descriptions has been already studied by means of molecular dynamics simulations [8,12,14,15,16]. An interesting finding in such direction for binary Lennard-Jones systems suggested a compelling picture for glassy dynamics [8]: the α-relaxation corresponds to a small number of fast crossings from one metabasin to a neighboring one involving the collective motion of a significant number of particles that form a relatively compact cluster, called "democratic cluster" or d-cluster.…”

Section: Introductionmentioning

confidence: 99%

Metabasin dynamics and local structure in supercooled water

et al. 2007

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We employ the Distance Matrix method to investigate metabasin dynamics in supercooled water. We find that the motion of the system consists in the exploration of a finite region of configuration space (enclosing several distinct local minima), named metabasin, followed by a sharp crossing to a different metabasin. The characteristic time between metabasin transitions is comparable to the structural relaxation time, suggesting that these transitions are relevant for the long time dynamics. The crossing between metabasins is accompanied by very rapid diffusional jumps of several groups of dynamically correlated particles. These particles form relatively compact clusters and act as cooperative relaxing units responsible for the density relaxation. We find that these mobile particles are often characterized by an average coordination larger than four, i.e. are located in regions where the tetrahedral hydrogen bond network is distorted.

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“…The discovery of dynamical heterogeneities in supercooled liquids and glasses provided a key to understand the relaxation dynamics of glassy systems [1,2]. Extensive molecular dynamics, MD, simulations in binary Lennard-Jones systems, LJ2, demonstrated that mobile particles are not homogeneously distributed in the sample but that they organize themselves in clusters [1].…”

Section: Introductionmentioning

confidence: 99%

Relaxation dynamics of simple glass‐formers: The role of timescale separation and activated dynamics at the metabasin level

Appignanesi

Fris

Alarcón

et al. 2005

phys. stat. sol. (c)

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PACS 61.20.Ja, 61.20.Lc, 64.70.Pf Within the landscape approach the dynamical heterogeneities presented by model glasses at low temperatures have been shown to represent well-defined elemental activated events in the exploration of the potential energy surface, PES. This last picture relies on the validity of a timescale separation hypothesis: Transitions within basins of attraction or Inherent Structures, ISs, of the PES must be fast compared to transitions between ISs. Additionally, ISs might be grouped in metabasins, MBs, the transition between them involving infrequent large scale rearrangements. In this work we clearly demonstrate the MB superstructure of the PES and study the T dependence of the MB dynamics. We find that beyond certain T timescale separation begins to break down both at the IS and the MB levels, which implies the cessation of the prevalence of activated dynamics as the system loses complexity, diversity and glassiness.

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Mechanistic view of the relaxation dynamics of a simple glass-former. A bridge between the topographic and the dynamic approaches

Cited by 9 publications

References 20 publications

Aging and intermittency in ap-spin model of a glass

Aging and intermittency in ap-spin model of a glass

Metabasin dynamics and local structure in supercooled water

Relaxation dynamics of simple glass‐formers: The role of timescale separation and activated dynamics at the metabasin level

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