Unveiling the effects of doping small nickel clusters with a sulfur impurity

Abstract

Small free-standing Ni clusters have been widely investigated during the last decade, but not many of their derived chalcogenides, despite their interest in technology and the new prospects that the nanoscale may open. The present work uncovers the effects of the S-doping on the structural, electronic, and magnetic properties of $\hbox {Ni}_n$, n = 1–10 clusters. Density functional theoretical calculations within the generalized gradient approximation for the exchange and correlation were conducted to explore the structural, electronic, and magnetic properties of the resulting $\hbox {Ni}_n\hbox {S}$ chalcogenide nanoparticles. The sulfur impurity is always adsorbed on the threefold hollow sites available on the nickel host, in qualitative agreement with recent results of S adsorption on Ni(111) surfaces. S-doping tends to enlarge the average Ni–Ni inter-atomic distance but enhances the thermodynamical stability of Ni clusters. It also increases the vertical ionization energy and electron affinity. However, S-doping has a small effect on the magnetism of small Ni clusters. According to the spin-dependent HOMO–LUMO gap, most of these clusters are good candidates as molecular junctions for spin filtering at low bias voltage.