Item

Abstract

In this work, we focus on low-dimensional colloidal model systems, via simulation studies and also
some complementary experiments, in order to elucidate the interplay between phase behavior,
geometric structures and transport properties. In particular, we try to investigate the (nonlinear!)
response of these very soft colloidal systems to various perturbations: uniform and uniaxial pressure,
laser fields, shear due to moving boundaries and randomly quenched disorder.
We study ordering phenomena on surfaces or in monolayers by Monte Carlo computer
simulations of binary hard-disk mixtures, the influence of a substrate being modeled by an external
potential. Weak external fie lds allow a controlled tuning of the miscibility of the mixture. We discuss
the laser induced de-mixing for the three different possible couplings to the external potential.
The structural behavior of hard spheres interacting with repulsive screened Coulomb or dipolar
interaction in 2D and 3D narrow constrictions is investigated using Brownian dynamics simulations.
Duc to misfits between multiples of the lattice parameter and the channel widths, a variety of
ordered and disordered lattice structures have been observed. The resulting local lattice structures
and defect probabilities are studied for various cross sections. The influence of a self-organized
order within the system is reflected in the velocity of the particles and their diffusive behavior.
Additionally, in an experimental system of dipolar colloidal particles confined by gravity on a
solid substrate we investigate the effect of pinning on the dynamics of a two-dimensional colloidal
liquid.
This work contains sections reviewing previous work by the authors as well as new,
unpublished results. Among the latter are detailed studies of the phase boundaries of the de-mixing
regime in binary systems in external light fields, configurations for shear induced effects at
structured walls, studies on the effect of confinement on the structures and defect densities in
three-dimensiona l systems, the effect of confinement and barriers on two-dimensional now and
diffusion, and the effect of pinning sites on the diffusion.