Finite-Size Effects on the Closest Packing of Hard Spheres

Abstract

We study closely packed crystalline structures formed by slow lateral compression of a colloidal suspension of hard spheres in a thin wedge. In addition to the known sequence of structural transitions, a buckling mechanism was recently proposed to maximize the packing fraction F between one and two layers. We here confirm this prediction experimentally and present the first evidence that for more than two layers, buckling, in this case of prism shaped arrays of particles, also takes place. This efficient mechanism may enhance F by up to 4% and dominates in major regions of the phase diagram.[ S0031-9007(97)

The wavelet response as a multiscale characterization of scattering processes at granular interfaces

“…We determine the bead concentration φ 0.63 by the volume of water needed to fill the dry medium pores: the result agrees with the concentration found for close random packing of glass beads [Page et al, 1995[Page et al, , 1996. Highest concentration of about 0.74 should be reached for arranged packings of spherical inclusions [Neser et al, 1997]. The glass beads are mixed into the water in order to suppress air bubbles; the surface of the layer is slightly smoothed to produce a flat reflector at the macroscopic scales and to avoid any ordered arrangement of the spheres [Sheng, 1995].…”

Melting of Colloidal Crystal Films

“…However, we observed that surface layers melt faster than bulk layers. We observed buckled phases or prism phases [9,26] at high volume fraction. Upon decreasing the volume fraction, the buckling disappeared and the domains became normal crystal; these normal crystals melted upon further lowering of the volume fraction.…”

Charged colloidal particles in a charged wedge: do they go in or out?

“…They are also known from gradients in solvent composition [26] or from gradients of temperature [27]. For confined suspensions, in particular, additional evaporation currents play a crucial role [28]. For large particles especially, sedimentation has to be considered, too.…”