Understanding fragility in supercooled Lennard-Jones mixtures. II. Potential energy surface

Coslovich, Daniele; Pastore, G.

doi:10.1063/1.2773720

Cited by 32 publications

(55 citation statements)

References 64 publications

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“…Production runs were performed using the Nose-Poincare thermostat [24]. Equilibration criteria were similar to the ones used in previous simulations of Lennard-Jones mixtures [25,26]. To improve the statistics and to average out small discrepancies in the actual pressure, three independent realizations were considered.…”

Section: Resultsmentioning

confidence: 99%

Heterogeneous slow dynamics and the interaction potential of glass-forming liquids

Coslovich

Roland

2011

Journal of Non-Crystalline Solids

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Section: Resultsmentioning

confidence: 99%

Heterogeneous slow dynamics and the interaction potential of glass-forming liquids

Coslovich

Roland

2011

Journal of Non-Crystalline Solids

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“…6(c) we plot the distribution of the participation ratio of unstable modes around T c . As in various conventional glass formers [47], the unstable modes of the KA mixture have small participation ratios and are therefore spatially localized. By contrast, the distribution is broader in the GCM and considerably shifted towards larger value of p (0.6 for plane waves, 1 for completely delocalized modes).…”

Section: Resultsmentioning

confidence: 99%

“…While determining the precise nature of the modes in the GCM would While determining the precise nature of the modes in the GCM would require an analysis of N -dependence of the spectrum, and thus of the mobility edge [48], our analysis suggests that the giant dynamic heterogeneities of the GCM might indeed be associated to these extended unstable modes. In the KA mixture, instead, dynamic heterogeneities build up through dynamic facilitation of localized elementary rearrangements [16], which might be related to modes localized outside locally stable domains [47].…”

Section: Resultsmentioning

confidence: 99%

Mean-field dynamic criticality and geometric transition in the Gaussian core model

2016

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We use molecular dynamics simulations to investigate dynamic heterogeneities and the potential energy landscape of the Gaussian core model (GCM). Despite the nearly Gaussian statistics of particles' displacements, the GCM exhibits giant dynamic heterogeneities close to the dynamic transition temperature. The divergence of the four-point susceptibility is quantitatively well described by the inhomogeneous version of the Mode-Coupling theory. Furthermore, the potential energy landscape of the GCM is characterized by a geometric transition and large energy barriers, as expected from the lack of activated, hopping dynamics. These observations demonstrate that all major features of mean-field dynamic criticality can be observed in a physically sound, three-dimensional model.

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“…1 The fragile behavior of viscosity is a problem of considerable interest to molecular-level calculations that attempt to sample the underlying potential energy surface ͑PES͒. 2, 3 While the minima of the PES ͑inherent structure͒ 4 and saddle points can be found by various numerical procedures, 3 no method yet exists that can compute the viscosity behavior over the range from 10 2 to 10 12 Pa s.…”

Section: Introductionmentioning

confidence: 99%

Computing the viscosity of supercooled liquids

Kushima

Lin

et al. 2009

The Journal of Chemical Physics

136

184

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We describe an atomistic method for computing the viscosity of highly viscous liquids based on activated state kinetics. A basin-filling algorithm allowing the system to climb out of deep energy minima through a series of activation and relaxation is proposed and first benchmarked on the problem of adatom diffusion on a metal surface. It is then used to generate transition state pathway trajectories in the potential energy landscape of a binary Lennard-Jones system. Analysis of a sampled trajectory shows the system moves from one deep minimum to another by a process that involves high activation energy and the crossing of many local minima and saddle points. To use the trajectory data to compute the viscosity we derive a Markov Network model within the Green-Kubo formalism and show that it is capable of producing the temperature dependence in the low-viscosity regime described by molecular dynamics simulation, and in the high-viscosity regime (10(2)-10(12) Pa s) shown by experiments on fragile glass-forming liquids. We also derive a mean-field-like description involving a coarse-grained temperature-dependent activation barrier, and show it can account qualitatively for the fragile behavior. From the standpoint of molecular studies of transport phenomena this work provides access to long relaxation time processes beyond the reach of current molecular dynamics capabilities. In a companion paper we report a similar study of silica, a representative strong liquid. A comparison of the two systems gives insight into the fundamental difference between strong and fragile temperature variations. We describe an atomistic method for computing the viscosity of highly viscous liquids based on activated state kinetics. A basin-filling algorithm allowing the system to climb out of deep energy minima through a series of activation and relaxation is proposed and first benchmarked on the problem of adatom diffusion on a metal surface. It is then used to generate transition state pathway trajectories in the potential energy landscape of a binary Lennard-Jones system. Analysis of a sampled trajectory shows the system moves from one deep minimum to another by a process that involves high activation energy and the crossing of many local minima and saddle points. To use the trajectory data to compute the viscosity we derive a Markov Network model within the Green-Kubo formalism and show that it is capable of producing the temperature dependence in the low-viscosity regime described by molecular dynamics simulation, and in the high-viscosity regime ͑10 2 -10 12 Pa s͒ shown by experiments on fragile glass-forming liquids. We also derive a mean-field-like description involving a coarse-grained temperature-dependent activation barrier, and show it can account qualitatively for the fragile behavior. From the standpoint of molecular studies of transport phenomena this work provides access to long relaxation time processes beyond the reach of current molecular dynamics capabilities. In a companion paper we report a similar study of ...

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Understanding fragility in supercooled Lennard-Jones mixtures. II. Potential energy surface

Cited by 32 publications

References 64 publications

Heterogeneous slow dynamics and the interaction potential of glass-forming liquids

Heterogeneous slow dynamics and the interaction potential of glass-forming liquids

Mean-field dynamic criticality and geometric transition in the Gaussian core model

Computing the viscosity of supercooled liquids

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