Atomistic study of vibrational properties of gamma-Al(2)O(3)
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2010-04Metadata
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Loyola, Claudia
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Atomistic study of vibrational properties of gamma-Al(2)O(3)
Abstract
A study of the vibrational density of states
(DOS) of c-Al2O3 is presented. Four structural models
from the recent literature are considered: vacant spinel
model and three nonspinel models. The vacant spinel and
one of the nonspinel models have unit cells with 40 atoms,
while the other two models have 160 atoms. The interatomic
interactions are computed using classical force
fields that include Coulomb and van der Waals attractive
interactions, short range repulsive interactions, as well as
three-body terms. The oxygen polarizability is included via
a core-shell potential. The DOS is compared with ab initio
calculations recently published for the vacant spinel model.
The classical and ab initio DOS show some differences for
frequencies higher than 200 cm-1, the ab initio having
more peaks and having a frequency cutoff 100 cm-1 lower
than the classical DOS. The DOS of all models present
some small differences. While the 160-atoms nonspinel
models present a rather structureless DOS, 40-atoms
models present peaks and dips relative to the 160-atoms
models. The elastic constants of polycrystalline c-Al2O3
are also estimated using several force fields. In general, the
classical force field predict higher elastic moduli than the
ab initio method. The infrared spectra of the four models
are calculated.
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Artículo de publicación ISI
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This work was supported by the Chile Bicentennial
Program of Science and Technology under Grant no. ACT/
ADI-24.
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JOURNAL OF MATERIALS SCIENCE, Volume: 45, Issue: 18, Pages: 5094-5100, 2010
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