Sommaire:

In supercooled liquids an effective temperature Teff can be defined through the fluctuation-dissipation relation, when the system is brought off-equilibrium in the glassy phase by a sudden temperature quench. We performed a study of a binary mixture of homonuclear Lennard- Jones dumbbells in and out of equilibrium, measuring Teff by perturbing both translational and rotational degrees of freedom, in order to investigate whether or not there is a Teff dependence on the observable chosen. For this purpose, we developed a code to perform Metropolis Monte Carlo simulations in the canonical ensemble. Moreover we implemented an efficient algorithm for measuring correlations and response functions under aging conditions. We performed our study at different elongations ζ of the molecules. Starting from ζ = 0.5 we found that the effective temperature of the rotational and translational degrees of freedom is the same. This occurs for a number of elongations above a critical elongation ζc that determines the transition from a strong steric hindrance scenario to a weak steric hindrance scenario. Below this critical elongation (ζ < ζc) we observed that the possibility to describe the system with only an effective temperature for both rotations and translations is quench-dependent.

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