Role of local structure on motions on the potential energy landscape for a model supercooled polymer

Jain, Tushar; Pablo, Juan J. de

doi:10.1063/1.1888505

Cited by 31 publications

(20 citation statements)

References 65 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Insights have also been realized using local measures of symmetry to elucidate local mobility, e.g. icosohedral order [11,14]; or the recent work of Shintani and Tanaka in which less mobile regions were shown to correlate well to structured, crystal-like domains [15]. Recently, the local Debye-Waller factor has been shown to correlate to the dynamic propensity [16], firmly establishing the connection between local dynamics at short and long times.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Structural and dynamical heterogeneity in a glass-forming liquid

2006

View full text Add to dashboard Cite

We use the "isoconfigurational ensemble" [Phys. Rev. Lett. 93, 135701 (2004)] to analyze both dynamical and structural properties in simulations of a glass forming molecular liquid. We show that spatially correlated clusters of low potential energy molecules are observable on the time scale of structural relaxation, despite the absence of spatial correlations of potential energy in the instantaneous structure of the system. We find that these structural heterogeneities correlate with dynamical heterogeneities in the form of clusters of low molecular mobility.PACS numbers: 64.70. Pf,05.60.Cd,61.43.Fs,81.05.Kf Over the last decade, the identification and study of dynamic heterogeneity (DH), especially in computer simulations, has added an important new dimension to our understanding of complex relaxation in glass forming liquids [1,2]. DH refers to the emergence and growth of spatially correlated domains of mobile and immobile molecules as temperature T approaches the glass transition temperature T g . A question that dominates research on DH concerns its connection to the structure of the liquid: What local configurational properties influence whether a given molecule is mobile or immobile?Recent work by Harrowell and Fynewever [3] has shown conclusively that a structuredynamics connection must exist at the molecular level.To do so, they use an "isoconfigurational (IC) ensemble" [3, 4, 5], a set of microcanonical molecular dynamics (MD) trajectories in which each run starts from the same initial equilibrium configuration, but with molecular momenta chosen randomly accordingly to a MaxwellBoltzmann distribution. The result is a set of trajectories lying on the same energy surface, and evolving away from their common initial point in configuration space. They then define and evaluate the "dynamic propensity": the average, in the IC ensemble, of the squared displacement of a molecule at a time comparable to the structural relaxation time. They show that DH is observed in this approach, in the form of increasing spatial correlations of the dynamic propensities in a glass forming liquid as T → T g . Since the influence of the initial momenta is averaged over, the observed spatial correlations must be configurational in origin.The strength of Ref.[3] is that it exposed the features of DH that are structural in origin, without needing to determine what structural properties are responsible. Other studies have worked towards explicitly identifying structural correlators to dynamics. A number of works over the past decades have identified relationships between average structural properties (especially free volume and measures of symmetry in the local molecular environment) and bulk dynamics; see e.g. Refs. [6,7,8,9]. More recently, several studies have sought a correlation at the microscopic level, e.g. between local free volume and local mobility, with more success in some systems [10,11] than in others [12]. A notable absence of correlation between the local volume and the local Debye-Waller factor has been report...

show abstract

mentioning

confidence: 99%

“…More recently, several studies have sought a correlation at the microscopic level, e.g. between local free volume and local mobility, with more success in some systems [10,11] than in others [12]. A notable absence of correlation between the local volume and the local Debye-Waller factor has been reported recently [13].…”

mentioning

confidence: 99%

Structural and dynamical heterogeneity in a glass-forming liquid

2006

View full text Add to dashboard Cite

show abstract

“…It was concluded that the proper inclusion of many-body static correlations in theories of the glass transition appears crucial for the description of the dynamics of fragile glass formers [56]. The search of a link between structural ordering and slow dynamics motivated several studies in liquids [57][58][59][60][61], colloids [62][63][64] and polymeric systems [62,[65][66][67][68][69][70]. We also note that the elastic models of the glass transition conclude that the relaxation is related to the elastic shear modulus, a quantity which is set by the arrangement of the particles in mechanical equilibrium and their mutual interactions [9,39].…”

Section: Introductionmentioning

confidence: 99%

Weak links between fast mobility and local structure in molecular and atomic liquids

Bernini

Puosi

Leporini

2015

The Journal of Chemical Physics

View full text Add to dashboard Cite

We investigate by Molecular-Dynamics simulations the fast mobility -the rattling amplitude of the particles temporarily trapped by the cage of the neighbors -in mildly supercooled states of dense molecular (linear trimers) and atomic (binary mixtures) liquids. The mixture particles interact by the Lennard-Jones potential. The non-bonded particles of the molecular system are coupled by the more general Mie potential with variable repulsive and attractive exponents in a range which is characteristic of small n-alkanes and n-alcohols. Possible links between the fast mobility and the geometry of the cage (size and shape) are searched. The correlations on a per-particle basis are rather weak. Instead, if one groups either the particles in fast-mobility subsets or the cages in geometric subsets, the increase of the fast mobility with both the size and the asphericity of the cage is revealed. The observed correlations are weak and differ in states with equal relaxation time. Local forces between a tagged particle and the first-neighbour shell do not correlate with the fast mobility in the molecular liquid. It is concluded that the cage geometry alone is unable to provide a microscopic interpretation of the known, universal link between the fast mobility and the slow structural relaxation. We suggest that the particle fast dynamics is affected by regions beyond the first neighbours, thus supporting the presence of collective, extended fast modes.

show abstract

“…Understanding how these these types of structural features connect to relaxation processes of supercooled liquids is an active area of research (see, e.g., Refs. 27,28,29,30).…”

Section: Introductionmentioning

confidence: 99%

Structural anomalies of fluids: Origins in second and higher coordination shells

et al. 2008

View full text Add to dashboard Cite

Compressing or cooling a fluid typically enhances its static interparticle correlations. However, there are notable exceptions. Isothermal compression can reduce the translational order of fluids that exhibit anomalous waterlike trends in their thermodynamic and transport properties, while isochoric cooling (or strengthening of attractive interactions) can have a similar effect on fluids of particles with short-range attractions. Recent simulation studies by Yan et al. [Phys. Rev. E 76, 051201 (2007)] on the former type of system and Krekelberg et al. [J. Chem. Phys. 127, 044502 (2007)] on the latter provide examples where such structural anomalies can be related to specific changes in second and more distant coordination shells of the radial distribution function. Here, we confirm the generality of this microscopic picture through analysis, via molecular simulation and integral equation theory, of coordination shell contributions to the two-body excess entropy for several related model fluids which incorporate different levels of molecular resolution. The results suggest that integral equation theory can be an effective and computationally inexpensive first-pass tool for assessing, based on the pair potential alone, whether new model systems are good candidates for exhibiting structural (and hence thermodynamic and transport) anomalies.

show abstract

Role of local structure on motions on the potential energy landscape for a model supercooled polymer

Cited by 31 publications

References 65 publications

Structural and dynamical heterogeneity in a glass-forming liquid

Structural and dynamical heterogeneity in a glass-forming liquid

Weak links between fast mobility and local structure in molecular and atomic liquids

Structural anomalies of fluids: Origins in second and higher coordination shells

Contact Info

Product

Resources

About