Superstructures of calcium carbonate crystals by oriented attachment

Crystalline hexagonal-shaped superstructures of calcium carbonate, synthesized in the presence of ammonia, are shown to be assembled by a three-dimensional oriented attachment of vaterite nanoparticles. This unusual crystallographic lock-in mechanism enables the formation of complicated rounded structures with a crystallographic orientation from nanosized building blocks, which has so far only been found for transition metal systems.