Dynamics of mixtures under confinement

Nunes, André

http://hdl.handle.net/10451/44156

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Autores

Nunes, André

Orientador(es)

Gama, Margarida Telo da

Resumo(s)

We study the self-organization of mixtures of colloidal particles in the presence of external fields and explore design strategies to obtain targeted structures. We consider two types of binary mixtures. In the first, the particles differ in their Stokes coefficient and in the second, the particles differ in their response to external fields. While for the first type the thermodynamic equilibrium state is completely mixed, for the second one, segregation is expected at equilibrium. Both types are characterized by having a complex energy landscape and, as a result, during the collective dynamics the systems get frequently trapped in local minima for long periods of time and so they rarely reach thermodynamic equilibrium within the timescale of relevance. The specific state in which the systems are kinetically arrested will depend strongly on the history. Thus, in order to properly simulate and characterize the dynamics of these systems, we need new methods and techniques. We employ particle based simulations such as Brownian Dynamics (BD) to probe the time evolution of the systems and Monte Carlo (MC) simulations to study the properties of the equilibrium states. We also use continuum models, including dynamical density functional theory of fluids (DDFT), to access long time scales that are not reachable with direct numerical simulations. We report the behavior in the presence of different spatially dependent external fields. We also show how mixtures of the first type can segregate while they are sedimenting under gravity. Finally, we propose a way to control the number of structural defects in crystals using random potentials in mixtures of the second type. Implications of our findings in the field of Soft Condensed Matter Physics are also discussed.