Glass-Specific Behavior in the Damping of Acousticlike Vibrations

Abstract

High frequency sound is observed in lithium diborate glass, Li2O-2B2O3, using Brillouin scattering of light and x rays. The sound attenuation exhibits a nontrivial dependence on the wave vector, with a remarkably rapid increase towards a Ioffe-Regel crossover as the frequency approaches the boson peak from below. An analysis of literature results reveals that the boson-peak frequency is closely related with a Ioffe-Regel limit for sound in many glasses. We conjecture that this relation, specific to glassy materials, might be rather common among them.

Neutron scattering investigation of high-frequency dynamics in glassy glucose

“…This peak is located at an almost constant energy, in an energy region typical of the boson peak (BP), as it will be also shown from the more detailed analysis. The comparison with experimental results on other systems and with moleculardynamics simulations 7,8,23 suggests the interpretation of this low-frequency feature as the high-frequency evolution of the transverse-acoustic mode. 25 However, it should be noted that the density fluctuation modes loose their symmetry as the wave vector is increased, so that the longitudinal and transverse terms have not a well defined significance.…”

“…In addition, a quasiperiodic trend of dispersion curves is often observed, 5,6 which recalls the phonon dispersion beyond the first Brillouin zone in crystals. As to the behavior of the peak broadening on varying the momentum transfer, a Q 4 dependence below 10 nm −1 is observed 7 for both random-network and molecular glasses, while a Q 2 dependence of the line width is observed in the nm −1 range. 8,9 These trends have been more recently enhanced in glycerol glass 10 observing the transition between Q 4 and Q 2 trends at about 2 nm −1 .…”

Polyamorphic transitions in Ce-based metallic glasses by synchrotron radiation

“…The broadening of acoustic excitations with increasing momentum transfer indicates an increase in the sound attenuation, up a point where the broadening becomes so large that it is no longer valid the term of propagating excitations to refer to the modes. 27 The energy of these acoustic-like excitations has a typical behavior of acoustic modes: it firstly increases with the increasing momentum transfer at low Q values and then starts to decrease when the highest Q values are reached, as displayed by the arrows in Fig. 3(a).…”

Scattering of acoustic phonons in disordered matter: A quantitative evaluation of the effects of positional versus orientational disorder

“…Here we show that thermal disorder significantly shortens the lifetimes of acoustic excitations within the ODC, which leads to significantly smaller heat conductivities, in agreement with experiment. To reconcile both results it is worth recalling that IXS ͑or INS͒ experiments carried out on polycrystals 5 mostly sample inhomogeneous spectra composed of excitations additional to those of acoustic character, 14 which preempts the interpretation of maxima and linewidths of the spectral bands in terms of physical frequencies and their damping terms.…”

“…On the other hand, our results may contribute to clarifying the nature of the spectral response observed by means of inelastic x-ray scattering ͑IXS͒ on polycrystals of the same material, 6 for which rather different interpretations have been proposed. 5,6 The measurements for the three solid phases were carried out under equilibrium vapor pressure at 2 -159 K by the steady-state potentiometric method using a special setup. 7 The preparation of the glass, disordered crystal, or fully ordered monoclinic phase was carried out following previously described procedures.…”