Slow dynamics of a confined supercooled binary mixture: direct space analysis

TL;DR

This study investigates the slow dynamics of a confined supercooled binary mixture through molecular dynamics simulations, revealing how confinement affects particle mobility, hopping processes, and the applicability of Mode Coupling Theory.

Contribution

It provides the first direct space analysis of supercooled binary mixtures under confinement, highlighting changes in dynamics and the limitations of Mode Coupling Theory in such systems.

Findings

Smaller particles avoid soft sphere interfaces at lower temperatures.

The mode coupling crossover temperature decreases under confinement.

Hopping processes are significantly enhanced above the crossover temperature.

Abstract

Dynamical properties of a Lennard-Jones binary mixture embedded in an off lattice matrix of soft spheres are studied in the direct space upon supercooling by molecular dynamics simulations. On lowering temperature the smaller particles tend to avoid the soft sphere interfaces and correspondingly their mobility decreases below the one of the larger particles. The system displays a dynamic behaviour consistent with the Mode Coupling predictions. A decrease of the mode coupling crossover temperature with respect to the bulk is found. We find however that the range of validity of the theory shrinks with respect to the bulk. This is due to the change in the smaller particle mobility and to a substantial enhancement of hopping processes well above the cross over temperature upon confinement.