FINITE-SIZE EFFECTS ON THE CLOSEST PACKING OF HARD-SPHERES

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 buckli ng mechanism was recently proposed to maximize the packing fraction Ph i between one and two layers. We here confirm this prediction experime ntally and present the first evidence that for more than two layers, b uckling, in this case of prism shaped arrays of particles, also takes place. This efficient mechanism may enhance Phi by up to 4% and domina tes in major regions of the phase diagram.