Low temperature behaviour and glass line of the symmetrical colloidal electrolyte

TL;DR

This study uses Molecular Dynamics simulations to explore the low temperature behavior and glass transition of a symmetrical colloidal electrolyte, revealing gelation, crowding, and glass formation mechanisms, with dynamics consistent with Mode Coupling Theory.

Contribution

It provides new insights into the arrest mechanisms and glass transition behavior of colloidal electrolytes, including the absence of re-entrant glass phenomena in such systems.

Findings

Gas-liquid coexistence at low T and ρ

Arrest due to gelation and crowding

Good agreement with Mode Coupling Theory predictions

Abstract

We report on the low temperature behaviour of the colloidal electrolyte by means of Molecular Dynamics simulations, where the electrostatic interactions were modeled using effective screened interactions. As in previous works, we have found a region of gas-liquid coexistence located in the low $T$- low $\rho$ region. At temperatures much lower than the critical one, the system cannot reach equilibrium, that is, the gas-liquid transition is arrested. Two different mechanisms have been identified to cause arrest: gelation in the lowest $T$ and crowding at intermediate $T$ values, the latter associated with the crossing point between the binodal and the glass line. To test the latter, the dynamics of the colloidal electrolyte near this crossing point has been computed and compared to the universal predictions of the ideal MCT. As in other glass-forming liquids, we found good agreement between this mean field theory and the dynamics of this complex system, although it fails just at the transition. Interestingly, in this region we found that the dynamics of this system is driven mainly by the steric interactions, showing all the typical properties of a repulsive colloidal glass. Finally, the isodiffusivity lines show that in this system with short range attractions, there is no re-entrant glass phenomenon, as opposed to monocomponent systems.