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Universal behavior of relaxational heterogeneity in glasses and liquids

D. Caprion·J. Matsui·H. R. Schober
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Abstract

We report an investigation of the heterogeneity in super-cooled liquids and glasses using the non-Gaussianity parameter. We simulate selenium and a binary Lennard-Jones system by molecular dynamics. In the non-Gaussianity three time domains can be distinguished. First there is an increase on the ps-scale due to the vibrational (ballistic) motion of the atoms. This is followed, on an intermediate time-scale, by a growth, due to local relaxations (beta-relaxation) at not too high temperatures. A maximum is reached at times corresponding to long range diffusion (alpha-relaxation). At long times the non-Gaussianity slowly drops, the system becoming homogeneous on these time-scales. In both systems studied, the non-Gaussianity follows in the intermediate time domain, corresponding to the beta-relaxations, a law ~ t^1/2. This general behavior is explained by collective hopping and dynamic heterogeneity. We support this finding by a model calculation.

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D. Caprion, J. Matsui, H. R. Schober. 2000-05-04. Universal behavior of relaxational heterogeneity in glasses and liquids. https://arxiv.org/abs/cond-mat/0005086

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