Dynamical properties of densely packed confined hard-sphere fluids

TL;DR

This study uses mode-coupling theory to analyze the dynamics of confined hard-sphere fluids, revealing complex relaxation behavior, non-monotonic dependence on confinement width, and agreement with molecular dynamics simulations.

Contribution

It provides a detailed numerical analysis of confined hard-sphere fluids using MCT, highlighting new non-trivial effects of confinement on dynamics and validating results with simulations.

Findings

Power-law decay in the $eta$-scaling regime

Non-monotonic dependence of exponents on slab width

Qualitative agreement with molecular dynamics simulations

Abstract

Numerical solutions of the mode-coupling theory (MCT) equations for a hard-sphere fluid confined between two parallel hard walls are elaborated. The governing equations feature multiple parallel relaxation channels which significantly complicate their numerical integration. We investigate the intermediate scattering functions and the susceptibility spectra close to structural arrest and compare to an asymptotic analysis of the MCT equations. We corroborate that the data converge in the $\beta$-scaling regime to two asymptotic power laws, viz. the critical decay and the von Schweidler law. The numerical results reveal a non-monotonic dependence of the power-law exponents on the slab width and a non-trivial kink in the low-frequency susceptibility spectra. We also find qualitative agreement of these theoretical results to event-driven molecular-dynamics simulations of polydisperse hard-sphere system. In particular, the non-trivial dependence of the dynamical properties on the slab width is well reproduced.