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Atomic Scale Modelling of Supported and Assembled Nanoparticles

Published online by Cambridge University Press:  14 March 2011

E. Zhurkin
Affiliation:
St.Petersbourg State Technical University, Department of experimental Nuclear Physics, Polytechnicheskaya 29, 195251, St.Petersbourg, Russia
M. Hou
Affiliation:
Physics of Irradiated Solids C.P.234, Free University of Brussels, B-1050 Brussels, Belgium
H.Van Swygenhoven
Affiliation:
Paul Scherrer Institute, Ch-5232 Villligen PSI, Switzerland
B. Pauwels
Affiliation:
EMAT, University of Antwerp, RUCA, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
M. Yandouzi
Affiliation:
EMAT, University of Antwerp, RUCA, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
D. Schryvers
Affiliation:
EMAT, University of Antwerp, RUCA, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
G.Van Tendeloo
Affiliation:
EMAT, University of Antwerp, RUCA, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
P. Lievens
Affiliation:
Laboratory for Solid State Physics and Magnetism, Catholic University of Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium
G. Verschoren
Affiliation:
Laboratory for Solid State Physics and Magnetism, Catholic University of Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium
J. Kuriplach
Affiliation:
Department of Low temperature Physics, Charles University, V. Holesovickach 2, CZ-18000 Prague 8, Czech Republic
S.Van Peteghem
Affiliation:
NUMAT, Subatomic and Radiation Physics Department, Ghent University, Proeftuinstraat 86, B-9000 Ghent, Belgium
D. Segers
Affiliation:
NUMAT, Subatomic and Radiation Physics Department, Ghent University, Proeftuinstraat 86, B-9000 Ghent, Belgium
C. Dauwe
Affiliation:
NUMAT, Subatomic and Radiation Physics Department, Ghent University, Proeftuinstraat 86, B-9000 Ghent, Belgium
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Abstract

The properties of elemental and bimetallic free, supported and assembled nanoclusters are modeled at the atomic scale and the models are discussed on the basis of experimental observations. This way, the memory of some free cluster properties in nanostructured materials may be evaluated.

The combination of molecular statics with High Resolution Transmission Electron Microscopy (HRTEM) allows to predict fine detail of the lattice relaxation of a truncated octahedral gold cluster deposited on MgO. Metropolis Monte Carlo (MC) predicts that a lattice mismatch may contribute to disordering in deposited Cu3Au nanoclusters. In both Cu-Au and Ni-Al free clusters, offset of equilibrium stoichiometry may result in segregation of Au or Al at the cluster surface. An ordered stoichiometric core is surrounded by a disordered mantle where the excess species resides. Different modeling methods predict different nanometer scale textures.

Therefore, cluster assembled Ni3Al alloys formed by condensation and pressing are modeled in two different ways. Both make use of a combination of Molecular Dynamics and MC. Whatever the model nanostructure, the segregation properties of free clusters remain in the nanostructured material. This segregation is one possible cause that can inhibit the formation of a metastable martensitic phase as observed in bulk Ni-Al alloys.

The occurrence of vacancy clusters and voids is hardly identified by HRTEM. On the other hand, their distribution and sizes are sensitive to the nanostructure modeling. Therefore, a new characterization method is developed, which combines positron lifetime spectroscopy with the calculation of positron lifetimes from selected areas of the model samples.

Type
Research Article
Copyright
Copyright © Materials Research Society 2001

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References

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