Arrested phase separation in a short-ranged attractive colloidal system: A numerical study

Abstract

We numerically investigate the competition between phase separation and dynamical arrest in a colloidal system interacting via a short-ranged attractive potential. Equilibrium fluid configurations are quenched at two different temperatures below the critical temperature and followed during their time evolution. At the lowest studied T, the phase-separation process is interrupted by the formation of an attractive glass in the dense phase. At the higher T, no arrest is observed and the phase-separation process proceeds endlessly in the simulated time window. The final structure of the glass retains memory of the interrupted phase-separation process in the form of a frozen spinodal decomposition peak, whose location and amplitude is controlled by the average packing fraction. We also discuss the time evolution of the nonergodicity parameter, providing evidence of a progressively decreasing localization length on increasing the packing fraction. Finally, we confirm that the reported results are independent of the microscopic dynamics.

Collective translational and rotational Monte Carlo moves for attractive particles

“…Similarly to what was originally reported [9], our preliminary results show that the VMMC algorithm is particularly useful in predicting the gelation boundary of low-and intermediate-density shortranged attractive systems below the critical point [27], where the density fluctuations [39], phase separation [40], or spinodal decomposition [41] lead to the formation of metastable droplets, fractal aggregates, or even stable clusters [28,31]. The cluster moves enhance the mobility of those structures which can kinetically slow down (arrest) and form glasses or gels.…”

Self-assembly and cooperative dynamics of a model colloidal gel network

“…In recent years a number of approaches for simulating colloidal gelation have been proposed, including shortrange isotropic interactions [21][22][23][24], valence-limited and patchy-particle models [25][26][27], dipolar particles [28], and anisotropic effective interactions [18,29,30]. We follow here this latter approach, using an effective interaction that includes, in the form of a three-body term, the basic ingredients for a minimal model of particle gels.…”

Self-diffusion of reversibly aggregating spheres

“…It leads to different equilibrium states depending on the volume fraction (φ) of the particles and the strength of the interaction energy (u). Weak attraction results in the formation of transient aggregates at low φ and a transient percolating network at high φ, while strong attraction may drive phase separation into a high and a low density liquid [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31]. The strength of the interaction and thus the equilibrium properties are determined by the ratio of the bond formation (α) and the bond breaking (β) probability [32,33,34,35,36,37,38,39,40,41,42,43,44,45], while the kinetics of such systems depend on the absolute values of α and β.…”