LAUSR

What makes things twist? Crystallization and chirality have been entangled since Pasteur's observations on chiral tartaric acid crystals, yet there is still limited understanding of how chiral compounds form chiral crystal morphologies. For example, although a chiral seed crystal can promote a particular handedness, it is not clear why such seeds do not do so with 100% efficiency. Ben-Moshe et al. examined chiral nanocrystals of tellurium grown from solution using various electron microscopy and diffraction techniques (see the Perspective by Popov). They found that screw dislocation- mediated growth is responsible for chiral polyhedral shape formation, and chiral crystals can thus form even in the presence of achiral ligands. Science, this issue p. 729; see also p. 688 The chiral shape of model inorganic nanocrystals arises through a screw dislocation mechanism. Despite persistent and extensive observations of crystals with chiral shapes, the mechanisms underlying their formation are not well understood. Although past studies suggest that chiral shapes can form because of crystallization in the presence of chiral additives, or because of an intrinsic tendency that stems from the crystal structure, there are many cases in which these explanations are not suitable or have not been tested. Here, an investigation of model tellurium nanocrystals provides insights into the chain of chirality transfer between crystal structure and shape. We show that this transfer is mediated by screw dislocations, and shape chirality is not an outcome of the chiral crystal structure or ligands.