Size Effect on the Atomistic Structure of Metallic Atom Clusters

Fujita, Hiroshi; Fujita, Naoya

doi:10.2320/matertrans.42.1474

Cited by 5 publications

(16 citation statements)

References 14 publications

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“…Furthermore, the specific surface energy is generally decreases by broad distribution within an atom cluster as cluster size decreases. 12) These are just the reverse results against the effect of surface tension mentioned above.…”

Section: Resultsmentioning

confidence: 53%

“…Therefore, each peripheral atom can move on the surface of Isphere, and thus each icosahedron transforms to a cuboctahedron without any thermal diffusion when constituent atoms increases in the number so that the electric charge is homogenized as a whole to reduce the difference in interatomic distances. 12) Electron microscope images do not show straight lattice fringes in the first stage when a Au-atom cluster is less than about È3 nm. 12) When cluster size becomes larger than about È3 nm, which belongs to the second stage, multiple straight lattice fringes showing a fcc-type structure appear.…”

Section: Resultsmentioning

confidence: 99%

“…12) Electron microscope images do not show straight lattice fringes in the first stage when a Au-atom cluster is less than about È3 nm. 12) When cluster size becomes larger than about È3 nm, which belongs to the second stage, multiple straight lattice fringes showing a fcc-type structure appear. At the beginning of this stage, however, contrast of peripheral regions of these clusters is not sharp, and takes a round shape without any facet structure.…”

Section: Resultsmentioning

confidence: 99%

“…[10][11][12] Each icosahedron generally has 12 coordination number around the center atom, in which interatomic distance between adjacent peripheral atoms is larger than that between the center atom and each peripheral one.…”

Section: Resultsmentioning

confidence: 99%

“…The author has reported [8][9][10][11][12][13] that when the size of Au-particles becomes smaller than the nucleus of crystal their behavior anomalously changes, and that the following three stages of atomistic structure occur before the nucleation of fcc crystals; Formation of (1) icosahedral structures, (2) cuboctahedral structures of a fcctype, and (3) embryo of the final crystal. Here, these nanometer sized materials are named ''atom clusters''.…”

Section: Introductionmentioning

confidence: 99%

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Three Stages of Bonding Mode before Nucleation of Metal Crystals

Fujita

2007

Mater. Trans.

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Effect of particle size on atomistic structures of vapor deposited Au-atom clusters has been examined by electron microscopy with the following results: (a) Icosahedrons are first formed, and they grow by two types of face sharing of further icosahedrons. (b) The lattice constant decreases more than about 1% in transition from icosahedral structures to cuboctahedral ones, which are a fcc-type structure, when average size of atom clusters becomes larger than about È3 nm. (c) Embryo of the final fcc structure is formed when the size of atom clusters increases to about È8 nm, and the lattice constant considerably increases more than 2% in spite of the same fcc structure as cuboctahedral ones. After that, the lattice constant scarcely changes even when the particle size increases more than È20 nm.These facts are considered to be closely related to heterogeneous distribution of electric charge within atom clusters. Based on the results, relationships between electronic structures in the three stages and anomalous behavior of metal-atom clusters, consisting of both fcc-type and bcc-type elements, are discussed.

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Section: Resultsmentioning

confidence: 53%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Three Stages of Bonding Mode before Nucleation of Metal Crystals

Fujita

2007

Mater. Trans.

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Physical Characteristics of Stabilized Silver Nanoparticles Formed Using a New Thermal-Decomposition Method

Nagasawa

Maruyama

Komatsu

et al. 2002

phys. stat. sol. (a)

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We decomposed a silver-fatty acid complex at 250 C in a nitrogen atmosphere to make stable, mono-disperse silver nanoparticles. The size distribution was measured using high-resolution transmission electron microscopy (HRTEM); the mean particle diameter was 4.7 nm and the standard deviation was 0.6 nm. This size distribution was verified by the measured surface-plasmon absorption spectrum. Their X-ray diffraction pattern showed that they were metallic silver. Then we examined their internal structure using HRTEM. The particles cross-sectional shapes were usually circular except some were hexagons or pentagons. According to the HRTEM image, most particles were multiple twins; 18% were simple twins and 2% were single crystals. Use of thermogravimetry and differential thermal analysis showed that their surface was coated by fatty acid. This coating stabilized the nanoparticles thus preventing their aggregation even after repeatedly dissolving them in solvent and evaporating. However, the coating was easily removed by baking at 210 C in one atmosphere of air.

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