Stable inter-Martensitic colloidal crystals

The recent progress made in controlling the synthesis of nanocrystals makes them highly tunable material building blocks, where the tailorability of particle shape, size, and surface chemistry enables the creation of new materials with emergent properties. The continued increase in particle synthesis capabilities has driven the appearance of increasingly complex superstructures obtained through self-assembly. Along these lines, a recent synthetic breakthrough has enabled the synthesis of polyhedral particles with a controllable degree of rounding, from polyhedral to spherical; self-assembly of these particles results in the formation of superlattices with shape-dependent structures that are intermediate between body-centered cubic (BCC) and face-centered cubic (FCC). That is, these particles can stabilize the intermediate structures along a Martensitic transformation. In this work, we elucidate the important features of the interparticle interactions that lead to the stability of Martensitic intermediates using a computational approach. We develop a model of shape-tunable nanocrystals that accounts for the shape of the particles as well as their ligand–ligand interactions. We find that in the hard shape limit, where ligand–ligand interactions are neglected, the intermediate structures are not stable and rapidly transition to either BCC or FCC structures. This work highlights the important role that capping ligands play in the self-assembly and stability of nanocrystal superlattices and motivates further work towards fine control over superlattice structure.