Scaling Analysis of Dynamic Heterogeneity in a Supercooled Lennard-Jones Liquid

Abstract

We have performed molecular dynamics computer simulations of a dense Lennard-Jones liquid mixture to study dynamic heterogeneity from normal liquid temperatures down to a supercooled temperature 15% above the previously identified mode-coupling temperature Tc of the model. A temperature-dependent correlation length associated with the correlation function of mobility fluctuations is calculated. The results are used to test two sets of scaling hypotheses for the dynamic heterogeneity. The results are in close agreement with the inhomogeneous mode-coupling theory of Biroli et al. [Phys. Rev. Lett. 97, 195701 (2006)] for both the alpha and beta relaxation regimes. Comparison with results for kinetically constrained models suggest that the Lennard-Jones mixture studied is more similar to models of fragile liquids than models of very strong liquids.

Analysis of a growing dynamic length scale in a glass-forming binary hard-sphere mixture

“…an Ornstein-Zernicke type fit; (2) set B=0 which gives a function suggested by the inhomogeneous mode-coupling theory [21]; (3) set A = χ 4 (t)| φ,c and C = 0, which results in a function suggested by field theoretic considerations [22,23]. We also fit S 4 (q; t) to a function utilized by Stein and Andersen [13], ln[S 4 (q; t)] = ln(A) − [ξq] 2 + Cq 4 , procedure (4). All of the fits results except for procedure (3) results in statistically the same length, Fig.…”

“…There were several earlier simulational investigations [10][11][12][13][14][15] of the correlation between the dynamic suscepti-bility χ 4 (t) and the correlation length ξ(t) and between the average dynamics (as characterized by, e.g. the α relaxation time, τ α ) and ξ(t), but their results, by and large, disagreed [28].…”

Microscopic aspects of Stretched Exponential Relaxation (SER) in homogeneous molecular and network glasses and polymers

“…Note that this application uses OTP (a large, planar organic polycylic molecule) to establish a length scale for small, tetrahedral H 2 O. Thus it appears that SER can be used to establish a topological length scale for glassy defects that is independent of host morphology (this is a question much-discussed in model simulations [33]); in itself, this is remarkable, as topology is generally supposed to describe only scaleindependent effects, but here it succeeds in handling length scales, presumably because of the compact nature of glassy configurations.…”

Hidden slow time scale of correlated motions in supercooled liquids: Multi-time correlation function approach

“…In other words, the correlations in dynamics can be measured in terms of four-point correlation functions and their associated dynamical susceptibility. In fact, the growing length scale of dynamical heterogeneity with decreasing temperature has been detected by recent numerical simulations [6,9,11,[14][15][16][17][18], experiments [19][20][21], and mode-coupling theory [22].…”