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Article Dans Une Revue Journal de Physique Année : 1984

Local elasticity properties of an amorphous structure : evidences for typical sites and shell structure ; dynamic stability

Résumé

Linear and quadratic Local Elasticity Coefficients (LEC) of non periodic structures are defined here. Assuming a macroscopic isotropy, the directions of local symmetry axes need not be considered, thus only 9 relevant LEC remain. This analysis applied to the ML amorphous structure shows that the local hydrostatic constraint p is uniform on each shell of atoms surrounding the centre of the structure, and takes only 5 different values for the 525 central atoms. Thus p defines 5 categories of sites and shells. The analysis of their other LEC confirms the existence of these 5 categories of shells which define bands of values for each of the LEC. Some internal structuration of the shells, i.e. subbands of LEC, is found Site categories are analysed in terms of local symmetry and topology. Atom dynamics are considered for possible localized modes with evidence for a softening of the frequencies of the modes more or less localized on a shell which encloses some 270 central atoms. These static and dynamics points of view enable us to make simple remarks on the magic numbers which are usual for shell structures. Global elastic properties such as bulk modulus and sound celerity for the ML structures, bare or filled with small, light atoms are derived, result in a ratio C11/C44 = 2.22, which is independent of the details of a short ranged pair interaction. This ratio is in good agreement with experimental data. Finally the size of frozen fluctuations is shown to be two or three interatomic distances: Applications to different kinds of interactions such as molecule-molecule or nucleon-nucleon interactions are suggested.
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jpa-00209755 , version 1 (04-02-2008)

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J.C.S. Levy, D. Mercier. Local elasticity properties of an amorphous structure : evidences for typical sites and shell structure ; dynamic stability. Journal de Physique, 1984, 45 (2), pp.291-301. ⟨10.1051/jphys:01984004502029100⟩. ⟨jpa-00209755⟩
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