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Titolo:
DO HIGH-FREQUENCY ACOUSTIC VIBRATIONS PROPAGATE IN STRUCTURALLY DISORDERED SOLIDS
Autore:
VACHER R; FORET M; COURTENS E; PELOUS J; SUCK JB;
Indirizzi:
UNIV MONTPELLIER 2,LAB VERRES,CNRS,UMRA 5587 F-34095 MONTPELLIER 5 FRANCE TECH UNIV CHEMNITZ ZWICKAU,INST PHYS D-09107 CHEMNITZ GERMANY
Titolo Testata:
Philosophical magazine. B. Physics of condensed matter.Statistical mechanics, electronic, optical and magnetic
fascicolo: 2, volume: 77, anno: 1998,
pagine: 523 - 532
SICI:
1364-2812(1998)77:2<523:DHAVPI>2.0.ZU;2-S
Fonte:
ISI
Lingua:
ENG
Soggetto:
BRILLOUIN-SCATTERING; VITREOUS SILICA; PHONON LOCALIZATION; THERMAL-CONDUCTIVITY; AMORPHOUS SOLIDS; GLASSES; MODES; ATTENUATION; CROSSOVER; FRACTONS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
43
Recensione:
Indirizzi per estratti:
Citazione:
R. Vacher et al., "DO HIGH-FREQUENCY ACOUSTIC VIBRATIONS PROPAGATE IN STRUCTURALLY DISORDERED SOLIDS", Philosophical magazine. B. Physics of condensed matter.Statistical mechanics, electronic, optical and magnetic, 77(2), 1998, pp. 523-532

Abstract

Glasses exhibit well known and apparently universal anomalies in their thermal properties. Their excess specific heat poses the question ofthe nature of the modes that contribute to the density of vibrationalstates and to the plateau in their thermal conductivity of the propagation of acoustic phonons. The vibrational modes involved in both anomalies must have frequencies well above 100 GHz, reaching into the terahertz range. This is a difficult region for direct spectroscopic observation of acoustic excitations. New small-angle inelastic neutron and inelastic X-ray scattering spectroscopies now give access to the structure factor S(Q,omega) in this region. Recent results on vitreous silica are discussed in the light of other well established spectroscopic information. We show in some detail that an elementary model, which consists in fitting inelastic spectra simply with a damped harmonic oscillator response, gives the impression that a mode continues to exist at frequencies omega above the strong phonon-scattering cross-over. It shows then, over some range of omega, an apparently constant velocity and a damping proportional to Q(2). Our present understanding, instead, is that the boson peak observed in S(Q,omega) relates to this strongscattering of the phonons by the structural disorder. The latter produces a cross-over from plane waves to non-propagating excitations which agrees with all the available information.

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Documento generato il 02/12/20 alle ore 17:33:45