Structural and electronic properties of Ni26-pXp clusters (X = Pd, Pt): A density-functional-theoretic study

We performed density-functional-theoretic calculations to investigate the structural, energetic, and electronic properties of the binary clusters Ni26-pXp (X = Pd, Pt) at T = 0 K. For small p, Pd and Pt clusters exhibit similar polyicosahedral structures and similar chemical order, the Pd or Pt atoms occupying positions with the lowest possible coordination numbers, forming "islands" separated from each other on the cluster surface. For intermediate and large p, there are marked differences between the Pd and Pt clusters. Notably, all the Ni26-pPdp clusters are polyicosahedral, whereas Ni26-pPtp clusters transition from polyicosahedral to cubic between p = 18 and p = 22. Also, whereas Pd atoms continue to constitute separated surface islands for as long as possible as p increases, until the islands eventually coalesce to form a shell surrounding an Ni core, Ni26-pPtp clusters transition from the "separated surface islands" configuration to the all-Pt structure via a series of configurations featuring Pt and Ni layers. (C) 2013 AIP Publishing LLC.