Amorphous solids, or glasses, are distinguished from crystalline solids by their lack of long-range structural order. At the level of two-body structural correlations, glassformers show no qualitative change upon vitrifying from a supercooled liquid. Nonetheless the dynamical properties of a glass are so much slower that it appears to take on the properties of a solid. While many theories of the glass transition focus on dynamical quantities, a solid's resistance to flow is often viewed as a consequence of its structure. Here we address the viewpoint that this remains the case for a glass. Recent developments using higher-order measures show a clear emergence of structure upon dynamical arrest in a variety of glass formers and offer the tantalising hope of a structural mechanism for arrest. However a rigorous fundamental identification of such a causal link between structure and arrest remains elusive. We undertake a critical survey of this work in experiments, computer simulation and theory and discuss what might strengthen the link between structure and dynamical arrest. We move on to highlight the relationship between crystallisation and glass-forming ability made possible by this deeper understanding of the structure of the liquid state, and emphasize the potential to design materials with optimal glassforming and crystallisation ability, for applications such as phase-change memory. We then consider aspects of the phenomenology of glassy systems where structural measures have yet to make a large impact, such as polyamorphism (the existence of multiple liquid states), aging (the time-evolution of non-equilibrium materials below their glass transition) and the response of glassy materials to external fields such as shear.Comment: 70 page
Recently, numerical evidence for a dynamical first-order phase transition in trajectory space [L.O. Hedges et al., Science 323, 1309 (2009)] has been found. In a model glass former in which clusters of 11 particles form upon cooling, we find that the transition has both dynamical and structural character. It occurs between an active phase with a high fraction of mobile and low fraction of cluster particles, and an inactive phase with few mobile but many cluster particles. The transition can be driven both dynamically and structurally with a chemical potential, showing that local order forms a mechanism for dynamical arrest.
We present quantitative experimental data on colloidal laning at the single-particle level. Our results demonstrate a continuous increase in the fraction of particles in a lane for the case where oppositely charged particles are driven by an electric field. This behavior is accurately captured by Brownian dynamics simulations. By studying the fluctuations parallel and perpendicular to the field we identify the mechanism that underlies the formation of lanes.Far from thermodynamic equilibrium, a wealth of fascinating selforganization processes can emerge along with unusual pattern formation and novel transport properties. 1,2 One of the simplest prototypes of non-equilibrium pattern formation is lane formation, exhibited by dusty plasmas, 3,4 granular matter, 5 pedestrian dynamics, 6,7 and army ants. 8 In this paper, we characterize the patterning and dynamical signatures of lane formation in a colloidal system experimentally and with computer simulations. Our results may find use in electronic ink, which also contains oppositely charged colloids that are driven by electric fields. 9,10 A fundamental and microscopic understanding of non-equilibrium phenomena requires resolving the underlying dynamical processes on the scale of the individual particles. For this, colloidal dispersions are excellent model systems since they can be brought out of equilibrium in a controlled way by external fields and the trajectories of the individual particles can be tracked in real space using confocal microscopy, which allows unparalleled comparison with computer simulation and particle-level theory. 11-13 Here, we first study the formation of lanes in driven colloidal mixtures as a function of the driving strength using both experiments and Brownian dynamics computer simulations. Lane formation in this 3D system is found to be a continuous process as a function of driving field. Starting from an initial mixed state, the dynamical mechanism behind the formation of lanes is identified: there is an enhanced lateral mobility of particles induced by collisions with particles driven in the opposite direction, which sharply decreases once lanes are formed. Therefore, particles in a lane can be regarded as being in a dynamically 'locked-in' state.In our experiments, we used a binary dispersion of sterically stabilized, nearly equal sized, but oppositely charged polymethylmethacrylate (PMMA) spheres inside a rectangular capillary. The particles were synthesized by dispersion polymerization, 14 and fluorescently labeled with either 7-nitrobenzo-2-oxa-1,3-diazole (NBD) or rhodamine isothiocyanate (RITC). The two species are color-coded as 'green' (s green ¼ 1.06 mm, polydispersity 6%, NBDlabeled) and 'red' (s red ¼ 0.91 mm, polydispersity 7%, RITC-labeled). The overall volume fraction of the suspension f green (0.090) + f red (0.090) was 0.18.To match the density and refractive index of the particles with the solvent, the particles were dispersed in a mixture of 27.2 w% cisdecahydronaphthalene and cyclohexylbromide containing 75 mM tetrabut...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.