Tuning the Glass Transition: Enhanced Crystallization of the Laves Phases in Nearly Hard Spheres.

Colloidal crystals with a diamond and pyrochlore structure display wide photonic band gaps at low refractive index contrasts. However, these low-coordinated and open structures are notoriously difficult to self-assemble from colloids interacting with simple pair interactions. To circumvent these problems, one can self-assemble both structures in a closely packed MgCu Laves phase from a binary mixture of colloidal spheres and then selectively remove one of the sublattices. Although Laves phases have been proven to be stable in a binary hard-sphere system, they have never been observed to spontaneously crystallize in such a fluid mixture in simulations nor in experiments of micron-sized hard spheres due to slow dynamics. Here we demonstrate, using computer simulations, that softness in the interparticle potential suppresses the degree of 5-fold symmetry in the binary fluid phase and enhances crystallization of Laves phases in nearly hard spheres.