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Résumé:

The dynamics of glass-forming liquids is heterogeneous and displays growing spatial correlations upon cooling. Whether such behavior arises from heterogeneities in local structure or more complex forms of amorphous order is a highly debated question. To clarify this issue, we study several model liquids within a coherent simulation framework based on the iso-configurational ensemble. We find that the correlation between the preferred local structure and dynamic heterogeneity is strongly system dependent. The correlation is pronounced in systems that deviate markedly from the mean-field picture of glassy dynamics and weak in models that adhere to it to a good extent. In the model that adheres best to the mean-field paradigm, namely a dense fluid of Gaussian particles, than nature of dynamic heterogeneity differs strikingly from the other liquids: on approaching the mode Coupling critical temperature the fluid develops giant dynamic fluctuations accompanied by nearly Gaussian single-particle dynamics. The observed differences between the models are qualitatively explained in terms of their potential energy landscapes.