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Structure and chemical ordering in CoPt nanoalloys (Articolo in rivista)

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Structure and chemical ordering in CoPt nanoalloys (Articolo in rivista) (literal)

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Rossi, G; Ferrando, R; Mottet, C (2008)
Structure and chemical ordering in CoPt nanoalloys
in Faraday discussions (Online)
(literal)

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http://pubs.rsc.org/en/Content/ArticleLanding/2008/FD/b705415g#!divAbstract (literal)

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\"[Mottet, C.] CRMCN CNRS, F-13288 Marseille, France; [Rossi, G.; Ferrando, R.] Univ Genoa, Dept Fis, IMEM CNR, I-16146 Genoa, Italy; [Rossi, G.; Ferrando, R.] Univ Genoa, INFM, I-16146 Genoa, Italy (literal)

Titolo

Abstract

The structure and chemical ordering of CoPt nanoclusters in the size range of 1 to 3 nm are investigated by global optimization methods and Monte Carlo simulations using a many body potential derived from the tight binding model. For the smaller systems (number of atoms N < 100), the optimized clusters display a polyicosahedral-like atomic structure with a little core-shell chemical ordering characterized by a particular surface chemical configuration: some pentagonal or hexagonal Pt rings centered, respectively on a Co atom or a Co dimer. A transition to the decahedral symmetry occurs at about N = 100 atoms, with a pseudo L1(0) ordered phase in each tetrahedral unit. For larger cluster sizes, 201 < N < 1289, the L1(0)-ordered/disordered transition on the face centered cubic truncated octahedron is studied by canonical Monte Carlo simulations showing that the critical disordering temperature decreases with the cluster size. We also notice a Co surface segregation especially at edges and, possibly, (100) facets, depending on the cluster size, on both cubic and fivefold symmetry structures. (literal)

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