Crossovers in the dynamics of supercooled liquids probed by an amorphous wall
GM Hocky and L Berthier and W Kob and DR Reichman, PHYSICAL REVIEW E, 89, 052311 (2014).
We study the relaxation dynamics of a binary Lennard-Jones liquid in the presence of an amorphous wall generated from equilibrium particle configurations. In qualitative agreement with the results presented by Kob et al. Nat. Phys. 8, 164 (2012). for a liquid of harmonic spheres, we find that our binary mixture shows a saturation of the dynamical length scale close to the mode-coupling temperature T-c. Furthermore we show that, due to the broken symmetry imposed by the wall, signatures of an additional change in dynamics become apparent at a temperature well above T-c. We provide evidence that this modification in the relaxation dynamics occurs at a recently proposed dynamical crossover temperature T-s > T-c, which is related to the breakdown of the Stokes-Einstein relation. We find that this dynamical crossover at T-s is also observed for the harmonic spheres as well as a WCA liquid, showing that it may be a general feature of glass-forming systems.
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