Shape variations and anisotropic growth of multiply twinned nanoparticles

Cyclic multiple twins as nanoobjects that display nearly regular polyhedron shape variety together with strongly anisotropic shape variations due to growth processes are reviewed with regard to their unique shape evolution based on the specific formation modes as well as on the particular structure of twin-related subunits. The review includes (i) the shape variations due to growth by stacking of tetrahedral Subunits, (ii) the role of growth conditions in the shape evolution of multiply twinned nanoparticles, and (iii) the modes of twin-based anisotropic growth including branching growth and unidirectional growth. The particular structures are introduced making use of electron microscopy structural characterization of multiply twinned metal nanoparticles as well as some nonmetal examples, and instructive models of the various configurations.