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Article Dans Une Revue The Journal of Chemical Physics Année : 2022

Theory of length-scale dependent relaxation moduli and stress fluctuations in glass-forming and viscoelastic liquids

Résumé

The spatiotemporal correlations of the local stress tensor in supercooled liquids are studied both theoretically and by molecular dynamics simulations of a two-dimensional (2D) polydisperse Lennard-Jones system. Asymptotically exact theoretical equations defining the dynamical structure factor and all components of the stress correlation tensor for low wave-vector q are presented in terms of the generalized ( q-dependent) shear and longitudinal relaxation moduli, G( q, t) and K( q, t). We developed a rigorous approach (valid for low q) to calculate K( q, t) in terms of certain bulk correlation functions (for q = 0), the static structure factor S( q), and thermal conductivity κ. The proposed approach takes into account both the thermostatting effect and the effect of polydispersity. The theoretical results for the ( q, t)-dependent stress correlation functions are compared with our simulation data, and an excellent agreement is found for [Formula: see text] (with [Formula: see text] being the mean particle diameter) both above and below the glass transition without any fitting parameters. Our data are consistent with recently predicted (both theoretically and by simulations) long-range correlations of the shear stress quenched in heterogeneous glassy structures.
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Dates et versions

hal-03806940 , version 1 (08-10-2022)

Identifiants

Citer

L. Klochko, J. Baschnagel, J. Wittmer, H. Meyer, O. Benzerara, et al.. Theory of length-scale dependent relaxation moduli and stress fluctuations in glass-forming and viscoelastic liquids. The Journal of Chemical Physics, 2022, 156 (16), pp.164505. ⟨10.1063/5.0085800⟩. ⟨hal-03806940⟩
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