The new challenging field of fabrication and interconnection of inorganic nanostructures is giving new impetus to the study of solid–solid interfacial properties. In nanocrystals made of two domains of different chemical composition and sharing an interface, the interfacial behavior is indeed critical for the stability of such an interface, and also in determining the mutual interactions of the two domains. Following a recent study by our group on the growth of colloidal nanocrystal heterodimers made of a domain of Au and a domain of CoPt 3, we report here an ab initio density functional theory study of the structural and electronic properties of Au/CoPt 3 interfaces. We have investigated the structure of different bulk CoPt 3 facets and of Au atoms adsorbed on CoPt 3. We calculated CoPt 3 and Au surface energies, Au/CoPt 3 interfacial energies as well as adsorption energies of Au atoms on CoPt 3 and Au, and we can draw …