After two decades of experimental and computational work, it is widely accepted that nanoscale confinement strongly perturbs the dynamics associated with glass formation. The presence of either a free surface or a non-wetting wall leads to a local enhancement of the dynamics, while strongly absorbing walls can slow the dynamics of glass formers. These qualitative trends have been observed in experiments through both direct and indirect measures of the dynamics, and simulations that directly measure the local mobility exhibit similar trends. However, there are several experimental observations that are qualitatively different from what is observed in simulations. In this talk, I will highlight these apparent discrepancies as well as describe our attempts at resolving them. Specific features that I will discuss include the sharp onset in confinement behavior that is often reported in experiments, the observation of a two-step relaxation function, and the strong cross-over in the activation energy as a function of film thickness.

Rationalizing simulations with experiments on the dynamics of confined glasses

254th National Meeting (2017)

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