Structural and electronic properties of Pt/Fe nanoclusters from EHT calculations

Extended Huckel theory (EHT) calculations are presented for pure Pt and mixed Pt/Fe nanoclusters, with a number of atoms in the range N-at = 13-309. Icosahedral and single-crystal (cuboctahedral, truncated octahedral) geometries are considered, optimized through a many-body potential approach for pure Pt clusters. In the mixed Pt/Fe clusters, the Fe atoms simply replace Pt atoms in an otherwise unrelaxed structure. It is found that single-crystal configurations are generally preferred over icosahedral ones and that - up to an Fe content of similar to 30% - the Fe atoms segregate in the interior of the cluster and the mixing reaction is exothermic. The electronic properties of the clusters are analyzed and are found to rapidly converge to a quasi-metallic behaviour for a number of atoms larger than similar to 150. The theoretical results are compared with the known experimental data on these systems. (C) 1999 Elsevier Science B.V. All rights reserved.