Assessing the utility of structure in amorphous materials

Wei, Dan; Yang, Jundi; Jiang, Minqiang; Dai, Lan-Hong; Wang, Yun-Jiang; Dyre, Jeppe C.; Douglass, Ian

doi:10.1063/1.5064531

Cited by 36 publications

(28 citation statements)

References 52 publications

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“…An important consequence of our finding is that the fragility is not affected by the attractive forces, but only by the repulsive ones which more directly control the local structure. This supports previous results which have linked the fragility to the emergence of locally favoured structures [31][32][33][34] and also to the steepness of the repulsive potentials [35]. While we do have shown in the SM [19] that our results are robust with respect to changes of the functional form of the attractive tails, we remain cautious about the generality of the role of attractive forces in the limit of very small attractive wells, where a re-entrant glass transition may occur [36].…”

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confidence: 92%

Role of Attractive Forces in the Relaxation Dynamics of Supercooled Liquids

Chattoraj

Ciamarra

2020

Phys. Rev. Lett.

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The attractive tail of the intermolecular interaction affects very weakly the structural properties of liquids, while it affects dramatically their dynamical ones. Via the numerical simulations of model systems not prone to crystallization, both in three and in two spatial dimensions, here we demonstrate that the non-perturbative dynamical effects of the attractive forces are tantamount to a rescaling of the activation energy by the glass transition temperature Tg: systems only differing in their attractive interaction have the same structural and dynamical properties if compared at the same value of T /Tg.According to the 'van der Waals picture' the physics of liquids is dominated by the harsh and short-ranged repulsive forces between the particles, the weaker and longer ranged attractive forces only providing a homogeneous cohesive background. This suggests the possibility of treating the attractive forces perturbatively, as first proposed by Weeks, Chandler and Andersen [1,2]. They indeed considered that, due the smooth spatial dependence of the attractive forces and the roughly homogeneous liquid structure, the sum of attractive forces experienced by a particle may be negligible with respect to the sum of the attractive ones. Hence 'the arrangements and motions of molecules . . . are determined primarily by the local packing and steric effects produced by the repulsive forces' [2]. Berthier and Tarjus [3,4] investigated the validity of this scenario focusing on the Kob-Andersen binary Lennard-Jones (KA-LJ) model [5], a prototypical glass former. To asses the relevance of the attractive forces, they compared this model with its WCA variant (KA-WCA), where particles interact via the purely repulsive potential obtained by truncating the LJ potential at its minimum. Their results demonstrated that the attractive forces have a non-perturbative effect on the relaxation dynamics, as the attractive forces greatly slow down the dynamics at low temperatures. Subsequent works have clarified that the difference between attractive and purely repulsive interactions could be attributed to the small structural differences induced by the attractive forces. These differences have been first identified in higher order structural correlations [6-9] and more recently, investigating two-point correlation functions via machine learning techniques [10]. Relating the relaxation time to the configurational entropy through the Adam-Gibbs relation [11], the effect of the different pair correlations on the dynamics has been rationalized considering their different contribution to the entropy [12][13][14]. It has also been demonstrated that it is possible to design a purely-repulsive potential that seemingly generates many structural and dynamical properties of LJ liquids [15][16][17].All of these results indicate that in molecular liquids the attractive forces do not have a perturbative effect as originally speculated. The open question ahead is therefore quantitatively rationalizing their non-perturbative influence. In this Letter, we c...

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supporting

confidence: 92%

Role of Attractive Forces in the Relaxation Dynamics of Supercooled Liquids

Chattoraj

Ciamarra

2020

Phys. Rev. Lett.

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“…The quantities defined in Eqs. (14) and (15) have analogues for the whole system (independent of community):…”

Section: Density Fluctuationsmentioning

confidence: 99%

“…Based on Eqs. (14) and (15) we define a joint probability distribution for r, k as in the main text:…”

Section: Single Speciesmentioning

confidence: 99%

“…Over the last years, computer simulations and experiments revealed the presence of more general locally stable motifs, known as "locally favored structures" (LFS), which can be detected using the Voronoi tessellation [5,6], topological cluster classification [7][8][9], bond orientational order analysis [10,11] and alternative approaches [12,13]. The emergence of well-defined locally favored structures suggests a reduction of structural diversity compared to the normal liquid [14] and hints to enhanced spatial variations of the preferred local order [15].…”

Section: Introductionmentioning

confidence: 99%

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Assessing the structural heterogeneity of supercooled liquids through community inference

Paret

Jack

Coslovich

2020

The Journal of Chemical Physics

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We present an information-theoretic approach inspired by distributional clustering to assess the structural heterogeneity of particulate systems. Our method identifies communities of particles that share a similar local structure by harvesting the information hidden in the spatial variation of two-or three-body static correlations. This corresponds to an unsupervised machine learning approach that infers communities solely from the particle positions and their species. We apply this method to three models of supercooled liquids and find that it detects subtle forms of local order, as demonstrated by a comparison with the statistics of Voronoi cells. Finally, we analyze the time-dependent correlation between structural communities and particle mobility and show that our method captures relevant information about glassy dynamics.

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“…In order to further quantify the diversity of structures and the configurational entropy, we introduce the concept of Shannon information entropy [41] associated with the incidence of local Voronoi structures (polyhedra) in disordered liquid and glass states [42], which reads…”

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confidence: 99%

Atomistic structural mechanism for the glass transition: Entropic contribution

et al. 2020

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A popular Adam-Gibbs scenario has suggested that the excess entropy of glass and liquid over crystal dominates the dynamical arrest at the glass transition with exclusive contribution from configurational entropy over vibrational entropy. However, an intuitive structural rationale for the emergence of frozen dynamics in relation to entropy is still lacking. Here we study these issues by atomistically simulating the vibrational, configurational, as well as total entropy of a model glass former over their crystalline counterparts for the entire temperature range spanning from glass to liquid. Besides confirming the Adam-Gibbs entropy scenario, the concept of Shannon information entropy is introduced to characterize the diversity of atomic-level structures, which undergoes a striking variation across the glass transition, and explains the change found in the excess configurational entropy. Hence, the hidden structural mechanism underlying the entropic kink at the transition is revealed in terms of proliferation of certain atomic structures with a higher degree of centrosymmetry, which are more rigid and possess less nonaffine softening modes. In turn, the proliferation of these centrosymmetric (rigid) structures leads to the freezing-in of the dynamics beyond which further structural adjustements become highly unfavourable, thus explaining the kink in the configurational entropy at the transition.

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Assessing the utility of structure in amorphous materials

Cited by 36 publications

References 52 publications

Role of Attractive Forces in the Relaxation Dynamics of Supercooled Liquids

Role of Attractive Forces in the Relaxation Dynamics of Supercooled Liquids

Assessing the structural heterogeneity of supercooled liquids through community inference

Atomistic structural mechanism for the glass transition: Entropic contribution

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