Potential energy landscape of a model glass former: Thermodynamics, anharmonicities, and finite size effects

Büchner, Stephan; Heuer, Andreas

doi:10.1103/physreve.60.6507

Cited by 190 publications

(268 citation statements)

References 35 publications

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“…Within a simulation this is indeed possible since one can investigate the relaxation dynamics of a given system for different system size (using periodic boundary conditions in all three directions). In the past such simulations have been done and it has been found that at a given temperature the relaxation dynamics slows down with decreasing temperature [77,78]. Hence we conclude that intrinsically confinement leads to a slower dynamics but that the presence of fluid-wall interactions can completely mask this general trend.…”

Section: Discussionmentioning

confidence: 94%

The Relaxation Dynamics of a Supercooled Liquid Confined by Rough Walls

2004

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We present the results of molecular dynamics computer simulations of a binary Lennard-Jones liquid confined between two parallel rough walls. These walls are realized by frozen amorphous configurations of the same liquid and therefore the structural properties of the confined fluid are identical to the ones of the bulk system. Hence this setup allows us to study how the relaxation dynamics is affected by the pure effect of confinement, i.e. if structural changes are completely avoided. We find that the local relaxation dynamics is a strong function of z, the distance of the particles from the wall, and that close to the surface the typical relaxation times are orders of magnitude larger than the ones in the bulk. Because of the cooperative nature of the particle dynamics, the slow dynamics also affects the dynamics of the particles for large values of z. Using various empirical laws, we are able to parameterize accurately the z−dependence of the generalized incoherent intermediate scattering function Fs(q, z, t) and also the spatial dependence of structural relaxation times. These laws allow us to determine various dynamical length scales and we find that their temperature dependence is compatible with an Arrhenius law. Furthermore, we find that at low temperatures time and space dependent correlation function fulfill a generalized factorization property similar to the one predicted by mode-coupling theory for bulk systems. For thin films and/or at sufficiently low temperatures, we find that the relaxation dynamics is influenced by the two walls in a strongly non-linear way in that the slowing down is much stronger than the one expected from the presence of only one confining wall. Finally we study the average dynamics of all liquid particles and find that the data can be described very well by a superposition of two relaxation processes that have clearly separated time scales. Since this is in contrast with the result of our analysis of the local dynamics, we argue that a correct interpretation of experimental data can be rather difficult.

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Section: Discussionmentioning

confidence: 94%

The Relaxation Dynamics of a Supercooled Liquid Confined by Rough Walls

2004

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“…) 2 , is proportional to T below T c , as expected from pure vibrations in quadratic wells, but the temperature dependence changes above T c , revealing "anharmonicities" in the landscape [23,24], see Fig. 1.…”

Section: Introductionmentioning

confidence: 94%

“…This has been interpreted as the sign that the landscape starts to "influence" the dynamical behaviour [23]. At T c , it is further argued, a second change in the landscape properties takes place, which is indicated by several observations [23,24,25,26,27,28,29]. For example, the mean-square displacement from an equilibrated configuration to its corresponding inherent struc-…”

Section: Introductionmentioning

confidence: 99%

Real space origin of temperature crossovers in supercooled liquids

2003

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We show that the various crossovers between dynamical regimes observed in experiments and simulations of supercooled liquids can be explained in simple terms from the existence and statistical properties of dynamical heterogeneities. We confirm that dynamic heterogeneity is responsible for the slowing down of glass formers at temperatures well above the dynamic singularity Tc predicted by mode coupling theory. Our results imply that activated processes govern the long-time dynamics even in the temperature regime where they are neglected by mode-coupling theory. We show that alternative interpretations based on topographic properties of the potential energy landscape are complicated and inefficient ways of describing simple physical features which are naturally accounted for within our approach. We show in particular that the reported links between mode coupling and landscape singularities do not exist.

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“…Qualitatively, one may say that TLS probe the PEL on a very local scale whereas for the understanding of the glass transition much larger regions of the PEL are relevant. Here we would like to mention that in recent years computer simulations succeeded in extracting many important features of the PEL of supercooled liquids [26,27,28,29,30,31,32,33,34].…”

Section: Introductionmentioning

confidence: 99%

Local properties of the potential-energy landscape of a model glass: Understanding the low-temperature anomalies

Reinisch

Heuer

2004

Phys. Rev. B

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Though the existence of two-level systems (TLS) is widely accepted to explain low temperature anomalies in the sound absorption, heat capacity, thermal conductivity and other quantities, an exact description of their microscopic nature is still lacking. We performed computer simulations for a binary Lennard-Jones system, using a newly developed algorithm to locate double-well potentials (DWP) and thus two-level systems on a systematic basis. We show that the intrinsic limitations of computer simulations like finite time and finite size problems do not hamper this analysis. We discuss how the DWP are embedded in the total potential energy landscape. It turns out that most DWP are connected to the dynamics of the smaller particles and that these DWP are rather localized. However, DWP related to the larger particles are more collective.

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Potential energy landscape of a model glass former: Thermodynamics, anharmonicities, and finite size effects

Cited by 190 publications

References 35 publications

The Relaxation Dynamics of a Supercooled Liquid Confined by Rough Walls

The Relaxation Dynamics of a Supercooled Liquid Confined by Rough Walls

Real space origin of temperature crossovers in supercooled liquids

Local properties of the potential-energy landscape of a model glass: Understanding the low-temperature anomalies

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