Finite-size effects in the diffusion dynamics of a glass-forming binary mixture with large size ratio

TL;DR

This study uses molecular dynamics simulations to explore how finite-size effects influence the diffusion behavior of particles in a large size ratio glass-forming mixture, revealing unexpected mobility patterns near the glass transition.

Contribution

It demonstrates the impact of finite-size effects on diffusion dynamics in a binary mixture with a large size disparity, linking these effects to collective interdiffusion behavior.

Findings

Large A particles undergo a glass transition near the mode coupling critical density.

Small B particles remain relatively mobile even at high densities.

Finite-size effects significantly influence the diffusion behavior of both particle types.

Abstract

Extensive molecular dynamics (MD) computer simulations of an equimolar glass-forming AB mixture with large size ratio are presented. While the large A particles show a glass transition around the critical density of mode coupling theory $\rho_c$, the small B particles remain mobile with a relatively weak decrease of their self diffusion coefficient $D_{\rm B}$ with increasing density. Surprisingly, around $\rho_c$, the self-diffusion coefficient of the A particles, $D_{\rm A}$, also starts to follow a rather weak dependence on density. We show that this is due to finite-size effects that can be understood from the analysis of the collective interdiffusion dynamics.