  Hierarchical self-assembly consisting of local associations of simple
building-blocks for the formation of complex structures widely exists in
nature, while the essential role of local assembly remains unknown. In this
work, by using computer simulations, we study a simple model system consisting
of associating colloidal hemispheres crystallizing into face-centered-cubic
crystals comprised of spherical dimers of hemispheres, focusing on the effect
of dimer formation on the hierarchical crystallization. We found that besides
assisting the crystal nucleation because of increasing the symmetry of
building-blocks, the association between hemispheres can also induce both
re-entrant melting and re-entrant crystallization depending on the range of
interaction. Especially when the interaction is highly sticky, we observe a
novel re-entrant crystallization of identical crystals, which melt only in
certain temperature range. This offers a new axis in fabricating responsive
crystalline materials by tuning the fluctuation of local association.
