Second-Row Transition-Metal Doping of (ZniSi), i = 12, 16 Nanoclusters: Structural and Magnetic Properties

Abstract

TM@ZniSi nanoclusters have been characterized by means of the Density Functional Theory, in which Transition Metal (TM) stands from Y to Cd, and i = 12 and 16. These two nanoclusters have been chosen owing to their highly spheroidal shape which allow for favored endohedral structures as compared to other nanoclusters. Doping with TM is chosen due to their magnetic properties. In similar cluster-assembled materials, these magnetic properties are related to the Transition Metal-Transition Metal (TM-TM) distances. At this point, endohedral doping presents a clear advantage over substitutional or exohedral doping, since in the cluster-assembled materials, these TM would occupy the well-fixed center of the cluster, providing in this way a better TM-TM distance control to experimentalists. In addition to endohedral compounds, surface structures and the TS’s connecting both isomers have been characterized. In this way the kinetic and thermal stability of endohedral nanoclusters is predicted. We anticipate that silver and cadmium endohedrally doped nanoclusters have the longest life-times. This is due to the weak interaction of these metals with the cage, in contrast to the remaining cases where the TM covalently bond to a region of the cage. The open-shell electronic structure of Ag provides magnetic properties to Ag@ZniSi clusters. Therefore, we have further characterized (Ag@Zn12S12)2 and (Ag@Zn16S16)2 dimers both in the ferromagnetic and antiferromagnetic state, in order to calculate the corresponding magnetic exchange coupling constant, J.This research was funded by Eusko Jaurlaritza (the Basque Government), and the Spanish Office for Scientific Research. The SGI/IZO-SGIker UPV/EHU (supported by Fondo Social Europeo and MCyT) is gratefully acknowledged for generous allocation of computational resources. JMM would like to thank Spanish Ministry of Science and Innovation for funding through a Ramon y Cajal fellow position (RYC 2008-03216). We thanks Elixabete Rezabal for cheerful discussion