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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. [ABSTRACT FROM AUTHOR]

We study the aging dynamics in a model for dense simple liquids, in which particles interact through a hard-core repulsion complemented by a short-ranged attractive potential, of the kind found in colloidal suspensions. In this system, at large packing fractions, kinetically arrested disordered states can be created both on cooling (attractive glass) and on heating (repulsive glass). The possibility of having two distinct glasses, at the same packing fraction, with two different dynamics offers the unique possibility of comparing—within the same model—the differences in aging dynamics. We find that, while the aging dynamics of the repulsive glass is similar to the one observed in atomic and molecular systems, the aging dynamics of the attractive glass shows novel unexpected features. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The role of sound in the dynamics of mesoscale systems is typically neglected, since frequently the associated time scales are much smaller than all the other time scales of interest. However, for sufficiently small objects embedded in a solvent with a sufficiently small sound velocity, sound can play a crucial role. In particular, behavior resembling viscoelasticity has been theoretically predicted for nonviscoelastic fluids. This effect is due to the interference of the propagation of sound waves caused by the solute particle’s motion and hydrodynamic vortex formation. We demonstrate this effect, known as backtracking, in computer simulations employing the method of multiparticle collision dynamics. We systematically study the influence of sound on the dynamics of the solute particle, and find that it disappears in the long-time limit. Thus, we confirm that sonic effects at the single-particle level can be neglected at sufficiently long times. [ABSTRACT FROM AUTHOR]

We discuss the phase behaviour of spherical hard-core particles, with an attractive potential, as described by a hard-core Yukawa model. The ratio of the range of the attraction to the diameter of the particles is an important control parameter of the problem. Upon decreasing the range of the attraction, the phase diagram changes quite significantly, with the liquid–gas transition becoming metastable, and the crystal being in equilibrium with the fluid, with no intervening liquid. We also study the glass transition lines and, crucially, find that the situation, being very simple for pure repulsive potentials, becomes much richer in competition between glass and crystal phases for short-range attractions. Also a transition between attractive and repulsive glass appears somewhat in analogy with the isostructural equilibrium transition between two crystals. [Copyright &y& Elsevier]