Out-of-equilibrium processes in suspensions of oppositely charged colloids: liquid-to-crystal nucleation and gel formation

• Published in: Journal of physics. Condensed matter 2008-12, Vol.20 (49), p.494247-494247 (10)
• Main Authors: Sanz, Eduardo, Valeriani, Chantal, Vissers, Teun, Fortini, Andrea, Leunissen, Mirjam E, van Blaaderen, Alfons, Frenkel, Daan, Dijkstra, Marjolein
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Physics
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/20/49/494247

We study the kinetics of the liquid-to-crystal transformation and of gel formation in colloidal suspensions of oppositely charged particles. We analyse, by means of both computer simulations and experiments, the evolution of a fluid quenched to a state point of the phase diagram where the most stable state is either a homogeneous crystalline solid or a solid phase in contact with a dilute gas. On the one hand, at high temperatures and high packing fractions, close to a substitutionally-ordered/stitutionally-disordered solid-solid coexistence line, we find that the fluid-to-crystal pathway does not follow the minimum free energy route. On the other hand, a quench to a state point far from the substitutionally-ordered/stitutionally-disordered crystal coexistence border is followed by a fluid-to-solid transition through the minimum free energy pathway. At low temperatures and packing fractions we observe that the system undergoes a gas -liquid spinodal decomposition that, at some point, stops, giving rise to a gel-like structure. Both our simulations and experiments suggest that increasing the interaction range favours crystallization over vitrification in gel-like structures.