Dynamic properties of quasi-confined colloidal hard-sphere liquids near the glass transition

Abstract

The complex behavior of confined fluids arising due to a competition between layering and local packing can be disentangled by considering quasiconfined liquids, where periodic boundary conditions along the confining direction restore translational invariance. This system provides a means to investigate the interplay of the relevant length scales of the confinement and the local order. We provide a mode-coupling theory of the glass transition (MCT) for quasi-confined liquids and elaborate an efficient method for the numerical implementation. The nonergodicity parameters in MCT are compared to computer-simulation results for a hard-sphere fluid. We evaluate the nonequilibrium-state diagram and investigate the collective intermediate scattering function. For both methods, nonmonotonic behavior depending on the confinement length is observed.

Impact of polydispersity and confinement on diffusion in hydrodynamically interacting colloidal suspensions

“…Also, it would be interesting to investigate the effects that incommensurate particle-size ratios and levels of confinement (Németh & Löwen 1999; Desmond & Weeks 2009; Schrack et al. 2020) have on the demixing, diffusivity, and, more interestingly, the promotion of glassy-like states of confined polydisperse colloidal suspensions.…”

Tagged-particle motion in quasi-confined colloidal hard-sphere liquids

“…The goal of the present work is to advance the analysis of quasi-confined liquids within the framework of MCT and with event-driven molecular dynamics simulations. The collective behavior has been discussed in detail recently [33]. Even in absence of layering a reentrance behavior is observed in the non-equilibrium state diagram, motivating us to further investigate these liquids, in particular with regard to the selfdynamics.…”

“…In this section, we convert the relevant MCT equations from the more general class of layered colloidal liquids [35] to quasi-confined fluids. For this purpose we basically follow reference [33] in which the corresponding collective equations have been derived. Since most of the steps of the derivation are identical if collective quantities are replaced by the corresponding single-particle quantities, we just provide a short summary of the main equations, focusing on the relevant differences to the collective case.…”

“…Liquid states then correspond to vanishing nonergodicity parameters, whereas F (s) µ (q) remains finite for glassy states. The nonergodicity parameters are directly accessible in simulations or experiments, and within the framework of MCT F (s) µ (q) can be determined without solving the full time-dependent equations explicitly [33,34].…”

“…As we have discussed previously [33], it is not practical to reach a fully equilibrated glassy fluid of polydisperse hard spheres in quasi-confinement, because as in the slit geometry [48], the particles will eventually demix and then crystallize. However, this process occurs on long timescales, outside what is experimentally relevant, and only accessible in simulations when relying on advanced, unphysical dynamical algorithms [8,49].…”