Biomedical subjects

F Baletto

Publications and source records attributed to F Baletto.

5 recordsLinked to original sources

PubMed2004

Magic polyicosahedral core-shell clusters.

A new family of magic cluster structures is found by genetic global optimization, whose results are confirmed by density functional calculations. These clusters are Ag-Ni and Ag-Cu nanoparticles with an inner Ni or Cu core and an Ag external shell, as experimentally observed for Ag-Ni, and present a polyicosahedral character. The interplay of the core-shell chemical ordering with the polyicosahedral structural arrangement gives high-symmetry clusters of remarkable structural, thermodynamic, and electronic stability, which can have high melting points (they melt higher than pure clusters of the same size), large energy gaps, and (in the case of Ag-Ni) nonzero magnetic moments.

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PubMed2004

Amorphization mechanism of icosahedral metal nanoclusters.

The amorphization mechanism of icosahedral Pt nanoclusters is investigated by a combination of molecular dynamics simulations and density functional calculations. A general mechanism for amorphization, involving rosettelike structural transformations at fivefold vertices, is proposed. In the rosette, a fivefold vertex is transformed into a hexagonal ring. We show that, for icosahedral Pt nanoclusters, this transformation is associated with an energy gain, so that their most favorable structures have a low symmetry even at icosahedral magic numbers, and that the same mechanism underlies the formation of amorphous structures in gold.

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PubMed2003

Growth of three-shell onionlike bimetallic nanoparticles.

We show by molecular dynamics simulations on three systems (B/A=Pd/Ag, Cu/Ag, and Ni/Ag) that three-shell metallic nanoparticles made by a core of a metal A, an intermediate shell of metal B and an external shell of metal A (A-B-A nanoparticles) can be grown by deposition of B atoms onto an A core. The growth of the intermediate B shell is triggered by the fact that the most favorable positions for isolated B impurities inside A clusters are located just one layer below the cluster surface.

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PubMed2002

Evidence of kinetic trapping in clusters of C60 molecules.

Molecular dynamics simulations of the growth of nanoclusters of C60 provide convincing evidence that experimental magic numbers, which are associated with structures based on Mackay icosahedra, are of kinetic origin. This finding resolves a long-standing contradiction between the experimental observations and the theoretically predicted most stable structures. Our results show that, even if a sticky intermolecular potential energetically disfavors icosahedral structures, the latter are frequently produced because the stickiness of the potential itself enhances kinetic trapping phenomena.

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PubMed2000

Reentrant morphology transition in the growth of free silver nanoclusters

The growth of free silver nanoclusters is studied by molecular dynamics simulations, from a small seed up to sizes N approximately 150. It is shown that the final outcome of the growth process depends crucially on the growth conditions (deposition flux straight phi and temperature T). A reentrant morphology transition is obtained: at intermediate values of T and straight phi a "decahedral window" is found; the window is surrounded by regimes where icosahedra are preferentially grown.

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