Structure of charged colloids under a wedge confinement

Monte Carlo simulations have been performed to study the influence of a wedge confinement by hard walls on the ordering of charged colloidal particles interacting through screened Coulomb repulsive potential in an aqueous medium. The density distribution of particles for a fixed wedge angle ${\theta }_0$ is studied for different suspension parameters, viz., bulk volume fraction $\phi ,$ salt concentration $C_s,$ and charge $\mathrm{Ze}$ on the particles. The density distribution $\rho \left(\theta \right)$ along the angular direction and that along the radial direction, $\rho \mathrm{}\left(r\right),$ have been analyzed in different regions of the wedge. Simulations show the formation of layered structure along the angular direction and a large gathering of particles along the wall. The number of layers as well as the density of particles within the layer are found to change as the strength and range of the interaction are varied, whereas the density profiles calculated close to the vertex region showed no significant variation in the density. The radial density profiles $\rho \mathrm{}\left(r\right)\mathrm{}$ corresponding to the vertex region show one-dimensional (1D) ordering of particles parallel to the vertex at a distance that is close to a wedge height, h equal to diameter of the particle. This 1D ordering is found to be destroyed upon the addition of salt or lowering the $\phi .$ The reported experimental observations on the “vacuum phase” are discussed in the light of the present results.