Kinetic crystallisation instability in liquids with short-ranged attractions

Abstract

Liquids in systems with spherically symmetric interactions are not thermodynamically stable when the range of the attraction is reduced sufficiently. However, these metastable liquids have lifetimes long enough that they are readily observable prior to crystallisation. Here we investigate the fate of liquids when the interaction range is reduced dramatically. Under these conditions, we propose that the liquid becomes kinetically unstable, i.e. its properties are nonstationary on the timescale of structural relaxation. Using molecular dynamics simulations, we find that in the square well model with range 6% of the diameter, the liquid crystallises within the timescale of structural relaxation for state points except those so close to criticality that the lengthscale of density fluctuations couples to the length of the simulation box size for typical system sizes. Even very close to criticality, the liquid exhibits significant structural change on the timescale of relaxation.

Real space analysis of colloidal gels: triumphs, challenges and future directions

“…Firstly, a larger polymer-colloid size ratio q means that, for a given degree of effective 'cooling' with respect to the critical point, by adding more polymer, corresponds to a colloidal liquid of lower volume fraction [24]. That is to say, if one adds (say) 10% more polymer than that corresponding to criticality, the volume fraction of the colloidrich phase is lower in the case of larger size ratio q. Secondly, if one reduces the concentration of polymer (approaching criticality), the volume fraction of the colloidal liquid decreases and, in principle, even very short-ranged effective attractions can result in colloidal liquids without arrest [199].…”