High-frequency phonon scattering in amorphous films

Long, A. R.; Cattell, A.F.; MacLeod, A M

doi:10.1016/0022-3093(80)90354-3

Cited by 8 publications

(2 citation statements)

References 13 publications

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“…In particular, for the thermal conductivity, a plateau at about 10 K is found to be superposed on a general increase of h with T. This and other features of the thermal properties are generally considered to be associated with the existence of low-energy, localized excitations, but detailed theoretical interpretation of the plateau is still controversial (12)(13)(14).…”

Section: Thermal Properties Of Nonmetallic Crystals Andmentioning

confidence: 99%

Clathrate and other solid phases in the tetrahydrofuran–water system: thermal conductivity and heat capacity under pressure

Ross¹,

Andersson²

1982

Can. J. Chem.

108

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RUSSELL G. Ross and PER ANDERSSON. Can. J. Chem. 60,881 (1982). Solid phases in the tetrahydrofuran-water (THF-H20) system were investigated in the temperature range 100-260K and at pressures up to 1.5 GPa. Thermal conductivity, h, and heat capacity per unit volume, pc,, were measured, using the transient hot-wire method. We made measurements on solid phases having nominal compositions THF.17H20, THF,7.1H20, and THF.4.6H20, which we refer to as phases a , P, and y , respectively. Phase a is known to be a structure I1 clathrate hydrate, and h for this phase was found to be similarto other crystalline solids which areglass-like in relation to their thermal properties. Low-energy excitations are known to be relevant to the properties of glass-like solids, and, in the case of phase a , were probably rotational vibrations of the THF guest molecules. Phase was similar, and we inferred that it was probably a structure I clathrate hydrate. Phase y behaved nearly like a normal crystal phase at low temperatures, but h became almost independent of temperature near melting. At 1.1 GPa and 130 K, we found evidence that phase a transformed, on pressurization, to a metastable modification which may be a new high-density form of clathrate hydrate. The astrophysical implications of our results were mentioned briefly. RUSSELL G. ROSS et PER ANDERSSON. Can. J. Chem. 60, 881 (1982). On a ttudie les phases solides dans le systkme tetrahydrofuranne-eau (THF-H20) dans un intewalle de temperature allant de 100 a 260 K et des pressions allant jusqu'a 1,s GPa. On a mesure la conductivite thermique, h, et la capaciti calorifique par unite de volume, pc,, en utilisant la methode du fil chaud transitoire. Nous avons effectue ces mesures sur des phases solides ayant des compositions nominales de THF.17H20, THF.7,1H20 et THF4,6H20 que nous disignons respectivement comme phases a,p et y.On sait que la phase a a une structure I1 d'hydrate de clathrate et on a trouvt que, pour cette phase, h est semblable a celui d'autres solides cristallins qui ressemblent des verres si I'on tient compte de leurs proprietes thermiques. On sait que les excitations de faible energie sont relikes aux proprietes des solides ressemblant a des verres et, dans le cas de la phase a, ce sont probablement des vibrations-rotations des molecules-h8tes de THF. La phase P est semblable et nous en diduisons qu'elle a probablement une structure I d'hydrate de clathrate. La phase y se comporte presque comme une phase cristalline normale a basse temperature, mais h devient presqu'indtpendant de la temperature au voisinage du point de fusion. A 1,l GPa et 130 K, nous avons trouve des indications a l'effet que la phase a se transforme, sous pression, en une forme metastable qui peut &tre une nouvelle forme d'hydrate de clathrate a haute densite. Nous mentionnons brikvement les implications astrophysiques de nos resultats.[Traduit par le journal]

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Section: Thermal Properties Of Nonmetallic Crystals Andmentioning

confidence: 99%

Clathrate and other solid phases in the tetrahydrofuran–water system: thermal conductivity and heat capacity under pressure

Ross¹,

Andersson²

1982

Can. J. Chem.

108

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“…These data will not be considered in the following discussion because they do not seem to be directly comparable with our measurements on bulk v-SiO 2 samples. It is worth noting that the TJ data are dominated by uncontrolled nonequilibrium and nonlinear effects [15] and that their interpretation is highly controversial, as similar independent measurements give results which differ up to a factor of 5 [16].…”

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confidence: 99%

Evidence for a Crossover in the Frequency Dependence of the Acoustic Attenuation in Vitreous Silica

et al. 2006

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We report measurements of the sound attenuation coefficient in vitreous silica, for sound waves of wavelength between 50 and 80 nm, performed with the new inelastic UV light scattering technique. These data indicate that in silica glass a crossover between a temperature-dependent (at low frequency) and a temperature-independent (at high frequency) acoustic attenuation mechanism occurs at Q 0:15 nm ÿ1 . The absence of any signature in the static structure factor at this Q value suggests that the observed crossover should be associated with local elastic constant fluctuations. DOI: 10.1103/PhysRevLett.97.035501 PACS numbers: 61.43.Fs, 63.50.+x The sound attenuation in disordered materials and its frequency and wavelength dependence are the result of the interplay between two physical mechanisms: one is due to the anharmonicity of the interparticle interactions, and the other to the structural disorder.The anharmonic attenuation of an acoustic sound wave, identified by its wavelength , frequency , and wave vector Q 2 = , is characterized by a specific, temperature-dependent, relaxation time r [1]. At low frequency (! r < 1) this process dominates the sound absorption through mechanisms such as, e.g., the Akhiezer mechanism [2,3]. Accordingly, the sound attenuation coefficient, as measured by the broadening ÿ of the Brillouin peak in the dynamic structure factor S Q; ! , scales as ! 2 and Q 2 . At high frequency ÿ! r > 1, i.e., Q > Q r 1=v r , where v is the sound velocity, the anharmonic attenuation becomes frequency independent [1][2][3].The sound attenuation associated with topological disorder gives rise to a steeper Q dependence of ÿ Q . If Rayleigh scattering is responsible for this attenuation, ÿ / Q 4 is expected for wavelengths larger than the typical defects size 2 =Q R . For Q > Q R , when the Rayleigh scattering regime is abandoned, one expects that ÿ Q is no longer / Q 4 . Experimentally, for Q larger than 1 nm ÿ1 , all glasses studied so far show ÿ / Q x , with x very close to 2 [4,5].This scenario can be summarized by a three-regime behavior of ÿ Q : (i) at low Q, ÿ Q is determined by anharmonic processes, and ÿ Q / Q 2 up to a first (temperature-dependent) crossover Q r 1=v r ; (ii) an intermediate regime, where the Q dependence of ÿ Q is determined by the system dependent strengths of anharmonicity and structural disorder processes; (iii) a high-Q regime, where ÿ Q is determined by the topological disorder and ÿ Q / Q 2 with a temperature-independent coefficient. This picture is highly debated because it critically depends on the location of Q r and Q R in different glasses. In densified v-SiO 2 , for example, the crossover Q R has been hypothesized to be around 2 nm ÿ1 [6].In the most studied case of vitreous silica, similarly to what happens in many other glasses, both Q r and Q R belong to a Q region which is not directly accessed by traditional scattering probes. In the case of v-SiO 2 , clear evidence is reported for the low-and high-Q quadratic behaviors of ÿ Q , using Brillouin light scat...

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