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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 4: Glasses and Glass Transition (joint session CPP/DY)
CPP 4.1: Hauptvortrag
Montag, 16. März 2020, 09:30–10:00, ZEU 255
Shear-stress fluctuations and relaxation in glassy liquids — Liudmyla Klochko, Ivan Kriuchevskyi, Joachim Wittmer, Alexander Semenov, Hendrik Meyer, and •Jörg Baschnagel — Institut Charles Sadron, University of Strasbourg & CNRS, 23 rue du Loess, 67034 Strasbourg Cedex, France
By means of molecular dynamics simulations we study the shear modulus µ and shear stress relaxation function G(t) of a short-chain glass-forming liquid. We determine µ via the shear-stress fluctuation formalism as a function of temperature T and sampling time Δ t. When cooling the system below the glass transition temperature Tg the shear modulus has a finite, T-dependent, value which depends on Δ t. We show that this sampling time dependence can be traced back to the relaxation of G(t), thereby establishing a relation between two often employed means—i.e. shear stress fluctuation formalism and G(t)—to characterize the shear response of glassy systems. We repeat the analysis for 100 independent configurations (samples) and find that the glass transition is accompanied by strong sample-to-sample fluctuations, implying that the standard deviation δ µ of the (ensemble-averaged) modulus displays a peak near Tg and is of the same order of magnitude as µ itself. We propose a theory which explains this behavior.