Geometry and Stability of “Spherical” f.c.c. Microcrystallites

Hoare, M. R.; Pal, Poorna C.

doi:10.1038/physci236035a0

Cited by 61 publications

(26 citation statements)

References 17 publications

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“…This is illustrated in Fig. 3 by the curve (5) in the case of Plate A. The failure of the kinematical theory in electron diffraction is to be expected for a mi cro crystal, speci ally one which consists of heavy atoms such as Pb ( z = 82), since the attenuation (o r extinction) V Ø f the original electron wave du e to interatom ic multiple acatterings (or dynamical interaction effects) is more import ant than that of X-ray , because of the stronger interaction between electror~ and atoms .…”

Section: Ii) Peak Intens I Tymentioning

confidence: 99%

Lead microclusters in the vapor phase as studied by molecular beam electron diffraction: Vestige of amorphous structure

Yokozeki¹

1978

The Journal of Chemical Physics

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The metal microclusters are formed in the gas phase by an isobaric cooling due to argon carrier gas, followed by adiabatic expansions through nozzle apertures. Electron diffraction patterns of these condensates show the typical Debye–Scherrer rings for the fcc Pb metal. The average size of clusters obtained, depending on the experimental conditions, ranges from 30 to 100 Å in diameter, and the cubic lattice parameters for these clusters are essentially the same, within an experimental error of 0.3%, as that for the bulk crystal. The analysis of the Bragg-peak intensities is carried out based on the usual kinematic theory and the dynamical (two-beam approximation) theory by Blackman. The former theory fails completely in accounting for small angle reflections (s≲5 Å−1), whereas the latter explains successfully the whole observe intensities, except for the second and third order reflections (400), (440), (333), and (600). From the damping of peak intensities the temperatures of these clusters are estimated to be of the order of 150 °K. A close inspection on the comparison between the observed and theoretical intensities, however, reveals periodic fluctuations in the observed peak heights as a function of the scattering angle, indicating a superposition of some diffuse scattering. The amplitudes of the fluctuations are more marked for the smaller size clusters. The characteristics of the fluctuations are accounted for by introducing liquidlike random atomic configurations into the microcrystalline. This model explains also the abnormal Bragg-peak intensities of Ar clusters reported in the literature.

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Section: Ii) Peak Intens I Tymentioning

confidence: 99%

Lead microclusters in the vapor phase as studied by molecular beam electron diffraction: Vestige of amorphous structure

Yokozeki¹

1978

The Journal of Chemical Physics

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“…We are really dealing with paths in (2N-3) dimensional configuration space and more elaborate methods are necessary for distinguishing maxima, minima, and saddle points. Finding the normal vibration spectrum (Hoare & Pal, 1972) will give information only on the local volume in configuration space in the neighbourhood of a given geometrical arrangement. Full molecular dynamic or Monte Carlo procedures are, as in three-dimensional space, in danger of'locking in' to a false minimum, and require some 'softening' of the hard sphere as a temporary measure.…”

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confidence: 99%

The closest packing of equal spheres on a spherical surface

Mackay¹,

Finney²,

Gotoh³

1977

Acta Cryst A

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“…This is a representative of a family of LJ n clusters whose potential energy surface can be described by the Lennard‐Jones potential and which serve as a model of, for example, noble gas clusters. The relative simplicity of Lennard‐Jones clusters and significant number of studies on their possible low‐energy structures up to n = 100015, 37–89 make them an excellent test system for various global optimization techniques. Lennard‐Jones clusters have been studied by means of genetic algoritms,51, 62, 64–67 various hypersurface deformation methods,68–75 annealing methods,15, 76–84 the “pivot method”,85–87 the “taboo search”,88, 89 and other techniques 90.…”

Section: Introductionmentioning

confidence: 99%