Chemical ordering patterns and magnetism of NiAl nanoclusters

We investigated the chemical ordering patterns and magnetism of face-centered cubic Ni x Al1−x nanoclusters having sizes 79 and 201 atoms and Ni concentrations x = 0, 0.25, 0.5, 0.75, and 1 using a combined basin hopping global sampling technique and spin-polarized density functional theory. The optimized nanoclusters display surface patterns with partially alloyed facets and a tendency for mixing. We also found a nonmagnetic to ferromagnetic phase transition at x = 0.75. This behavior is explained in terms of the distribution of the Ni atoms on the surface/subsurface region and local Ni clustering.