Atom ordering in cuboctahedral Ni–Al nanoalloys

Energy calculations have been carried out on high-symmetry cuboctahedral Ni–Al nanoalloy clusters, of varying composition, with the interatomic interactions modelled by the Gupta many-body potential. Relaxations of cuboctahedral fragments cut from the bulk lattice of Ni3Al, with 13–561 atoms, were undertaken, as were relaxations of high symmetry clusters with 55 and 147 atoms. The lowest energy isomers were found to be dominated by three factors: the tendency toward mixing due to the favourable energy of mixing, ΔmixE; the size difference between nickel and aluminium; and the higher cohesive and surface energy of nickel compared to aluminium. The latter two factors favour Al-segregation to the surface. The most stable Ni:Al composition approaches 3:1 for larger clusters.

Graphical abstractEnergy calculations, using the Gupta many-body potential, have been carried out on cuboctahedral geometric shell Ni–Al clusters (nanoalloys) with up to 561 atoms. The competition between exothermic Ni–Al mixing and size and surface energy effects, and their effect on the atomic distribution of the Ni and Al atoms have been investigated.Figure optionsDownload full-size imageDownload as PowerPoint slide