DENDRITIC GROWTH OF HARD-SPHERE CRYSTALS

Recent observations of the disorder-order transition for colloidal har d spheres under microgravity revealed dendritic crystallites roughly 1 -2 mm in size for samples in the coexistence region of the phase diagr am. Order of magnitude estimates rationalize the absence of large or d endritic crystals under normal gravity and their stability to annealin g in microgravity. A linear stability analysis of the Ackerson and Sch atzel model for crystallization of hard spheres establishes the domain of instability for diffusion-limited growth at small supersaturations . The relationship between hard sphere and molecular crystal growth is established and exploited to relate the predicted linear instability to the well-developed dendrites observed.