Theoretical study of Ni–Al nanoalloy clusters using particle swarm optimisation algorithm

The global structural optimisations for Ni–Al nanoalloy clusters at different compositions have been investigated using particle swarm optimisation combined with simulated annealing method. The second moment approximation of the tight binding potential has been used in describing the interatomic interactions. Some stable structures were obtained for Ni_xAl_x(x=1–8), Ni_3xAl_x(x=1–4) and Ni_xAl_3x(x=1–4) nanoalloy clusters. The simulation results show that the lowest energy isomers of nanoalloy clusters with the approximate composition ‘NiAl, Ni₃Al and NiAl₃‘ generally have structures based on icosahedral packing. It is confirmed that segregation is favoured for Ni–Al nanoalloy clusters, with the surface becoming richer in Al and the core becoming richer in Ni.