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Titolo:
Atomic structure and vibrational properties of icosahedral alpha-boron andB4C boron carbide
Autore:
Vast, N; Besson, JM; Baroni, S; Dal Corso, A;
Indirizzi:
CEA, Solides Irradies Lab, F-91128 Palaiseau, France CEA Palaiseau France F-91128 des Irradies Lab, F-91128 Palaiseau, France CEA, Ctr Etud Bruyeres, F-91680 Bruyeres Le Chatel, France CEA Bruyeres Le Chatel France F-91680 F-91680 Bruyeres Le Chatel, France Univ Paris 06, UMR CNRS 7602, F-75252 Paris, France Univ Paris 06 Paris France F-75252 UMR CNRS 7602, F-75252 Paris, France Scuola Int Super Studi Avanzati, I-34014 Trieste, Italy Scuola Int Super Studi Avanzati Trieste Italy I-34014 014 Trieste, Italy INFM, I-34014 Trieste, Italy INFM Trieste Italy I-34014INFM, I-34014 Trieste, Italy ENS, Ctr Europeen Calcul Atom & Mol, F-69007 Lyon, France ENS Lyon France F-69007 Europeen Calcul Atom & Mol, F-69007 Lyon, France Ecole Polytech Fed Lausanne, Inst Romand Rech Numer Phys Mat, CH-1015 Lausanne, Switzerland Ecole Polytech Fed Lausanne Lausanne Switzerland CH-1015 ne, Switzerland
Titolo Testata:
COMPUTATIONAL MATERIALS SCIENCE
fascicolo: 2-4, volume: 17, anno: 2000,
pagine: 127 - 132
SICI:
0927-0256(200006)17:2-4<127:ASAVPO>2.0.ZU;2-L
Fonte:
ISI
Lingua:
ENG
Soggetto:
NEUTRON POWDER DIFFRACTION; LATTICE-DYNAMICS; LIQUID BORON; CARBON-ATOMS; PRESSURE; CHAINS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
24
Recensione:
Indirizzi per estratti:
Indirizzo: Vast, N CEA, Solides Irradies Lab, F-91128 Palaiseau, France CEA Palaiseau France F-91128 dies Lab, F-91128 Palaiseau, France
Citazione:
N. Vast et al., "Atomic structure and vibrational properties of icosahedral alpha-boron andB4C boron carbide", COMP MAT SC, 17(2-4), 2000, pp. 127-132

Abstract

The Raman and infrared spectra of a-rhombohedral boron B-12 and of B4C boron carbide have been determined by accurate first-principles calculations based on density-functional perturbation theory. Our results account for allthe features observed experimentally, including the characteristic Raman-active mode around 530 cm(-1), which is attributed to the libration of the icosahedra. A comparison of the calculated vibrational spectra with experimental data allows the first unambiguous determination of the atomic structure of B4C, Analysis of our data shows that the high bulk moduli of cc-rhombohedral boron and of B4C boron carbide - 220 and 240 GPa, respectively - aremainly determined by the stiff intramolecular bonding within each icosahedron. This finding is at variance with the current interpretation of recent neutron diffraction data on B4C in terms of a postulated larger stiffness of the intermolecular bonds in icosahedral solids (inverted molecular compressibility). Our results show that icosahedral boron-rich solids should be considered as members of a new class of covalently bonded materials. (C) 2000 Elsevier Science B.V. All rights reserved.

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Documento generato il 08/04/20 alle ore 23:21:56