Charge and Salt Driven Reentrant Order-Disorder and Gas-Solid Transitions in Charged Colloids

TL;DR

This study uses Monte Carlo simulations to explore charge and salt effects on phase transitions in charged colloids, revealing reentrant order-disorder and gas-solid-like transitions consistent with experiments.

Contribution

It demonstrates the occurrence of reentrant order-disorder and gas-solid-like transitions in charged colloids through detailed simulation analysis.

Findings

Reentrant solid-liquid transition with increasing charge density.

Inhomogeneous to homogeneous transition upon salt addition.

Observation of gas-solid-like transition in colloids.

Abstract

Monte Carlo simulations have been performed for aqueous charged colloidal suspensions as a function of charge density on the particles and salt concentration. We vary the charge density in our simulations over a range where a reentrant solid-liquid transition in suspensions of silica and polymer latex particles has been reported by Yamanaka et al. [Phys. Rev. Lett. 80 5806 (1998)]. We show that at low ionic strengths a homogeneous liquid-like ordered suspension undergoes crystallization upon increasing charge density . Further increase in charge density resulted once again a disordered state which is in agreement with experimental observations. In addition to this reentrant order-disorder transition, we observe an inhomogeneous to homogeneous transition in our simulations when salt is added to the disordered inhomogeneous state. This inhomogeneous to homogeneous disordered transition is analogous to the solid-gas transition of atomic systems and has not yet been observed in charged colloids. The reported experimental observations on charged colloidal suspensions are discussed in the light of present simulation results.