A novel structural motif for free CoPt nanoalloys

The growth of small free platinum-cobalt nanoclusters has been modelled through the one-by-one atom deposition technique based on classical Molecular Dynamics. A novel structural motif, reminiscent of two stacked poly-icosahedral pancakes, has been found in close competition with a Marks-decahedron and a face-centred-cubic geometry at around 75 atoms for a cobalt-rich stoichiometry. The results have been confirmed at the density-functional level, which reveals an unexpected stability of this new morphology over a wide range of chemical compositions. Magnetic properties have been also discussed.