2000/05/04 by D. Caprion, Caprion, D., J. Matsui +3
Physics and Astronomy · #Disordered Systems and Neural Networks (cond-mat.dis-nn) #FOS: Physical sciences #cond-mat.dis-nn
paper · pdf · doi:10.48550/arxiv.cond-mat/0005086
arxiv created 2000/05/04 · arxiv updated 2009/11/30
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 ~ t1/2. This general behavior is explained by collective hopping and dynamic heterogeneity. We support this finding by a model calculation.