Colloidal and metallic liquids in and out of equilibrium_

Colloidal and metallic liquids in and out of equilibrium

The liquid state is central to two great challenges of condensed matter: crystallisation and dynamical arrest. We will consider the role of local structure in both. Due to the simplicity in their interactions, colloidal model systems form an ideal complement to computer simulation in tackling these problems. However, in crystallisation, the only system for which quantitative data exists, colloidal « hard » spheres, experiment and simulation disagree wildly. Meanwhile in dynamical arrest, the role of structure (if any) is highly controversial.

We introduce a novel structural analysis to tackle both crystallisation and dynamical arrest. Applying our methods to dynamical arrest, we find a clear structural mechanism for gelation. For the glass transition, we find clear structural changes which reveal a fundamental difference between these two modes of dynamical arrest: gelation is (quasi) first-order and vitrification is continuous. We further explore the effect of particle shape: a modest degree of anisotropy profoundly influences the energy landscape, leading to extreme kinetic trapping. Furthermore, based on this identification of local structure as an order parameter for vitrification, we introduce a new method by which a combination of structure and dynamics induces vitrification without quenching. Finally, in the case of crystallization of hard spheres after a careful comparison between experiment and simulation, we find good agreement between experiment and simulation.

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