Phonon interpretation of the ‘boson peak’ in supercooled liquids

Grigera, Tomás S.; Martı́n-Mayor, V.; Parisi, Giorgio; Verrocchio, P.

doi:10.1038/nature01475

Cited by 330 publications

(288 citation statements)

References 30 publications

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“…Having in mind that g D ͑ ͒ ϰ 2 , it is clear from the shape of these plots that the frequency distribution of g͑ ͒ exc corresponds approximately to convexlike tails. This form is consistent with recent predictions of the Euclidean random matrix theory, 65,66 as already noticed by Yannopoulos et al 16 The change in the maximum frequency of the Boson peak when Rb + are replaced by K + ions in the studied glasses can be attributed to at least two contributions. Firstly, the g͑ ͒ exc may shift towards higher frequency in the KMWPO glass due to "strengthening" of the involved vibrational modes.…”

Section: -7supporting

confidence: 92%

Heat capacity, Raman, and Brillouin scattering studies of M2O–MgO–WO3–P2O5 glasses (M=K,Rb)

Mączka

Hanuza

Baran

et al. 2006

The Journal of Chemical Physics

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The authors report the results of temperature-dependent Brillouin scattering from both transverse and longitudinal acoustic waves, heat capacity studies as well as room temperature Raman scattering studies on M 2 O-MgO-WO 3 -P 2 O 5 glasses ͑M=K,Rb͒. These results were used to obtain information about structure and various properties of the studied glasses such as fragility, elastic moduli, ratio of photoelastic constants, and elastic anharmonicity. They have found that both glasses have similar properties but replacement of K + ions by Rb + ions in the glass network leads to decrease of elastic parameters and P 44 photoelastic constant due to increase of fragility. Based on Brillouin spectroscopy they show that a linear correlation between longitudinal and shear elastic moduli holds over a large temperature range. This result supports the literature data that the Cauchy-type relation represents a general rule for amorphous solids. An analysis of the Boson peak revealed that the form of the frequency distribution of the excess density of states is in agreement with the Euclidean random matrix theory. The reason of the observed shift of the maximum frequency of the Boson peak when K + ions are substituted for Rb + ions is also briefly discussed.

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Section: -7supporting

confidence: 92%

Heat capacity, Raman, and Brillouin scattering studies of M2O–MgO–WO3–P2O5 glasses (M=K,Rb)

Mączka

Hanuza

Baran

et al. 2006

The Journal of Chemical Physics

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“…However a Γ ∝ ω 2 ∝ q 2 dependence is hypothesized for both mechanisms [3,7,17,18,27]. Such a Γ ∝ ω 2 ∝ q 2 dependence valid up to high q, has also been predicted by molecular dynamic simulations performed on realistic v-SiO 2 [28], on harmonic glasses [29] as well as on hard spheres systems [21] and disordered linear chains [30]; it is also supported by recent theoretical free-energy landscape studies [31,32]. BLS and IXS technique do not cover the entire frequency (and q) range from GHz to THz and investigations within the frequency gap which separates these techniques could be useful to discriminate between the different hypotheses.…”

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confidence: 65%

Sound attenuation in a unexplored frequency region: Brillouin ultraviolet light scattering measurements inv−SiO2

et al. 2005

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We report Ultraviolet Brillouin light scattering experimental data on v-SiO2 in an unexplored frequency region, performed with a newly available spectrometer up to exchanged wavevector q values of 0.075 nm −1 , as a function of temperature. The measured attenuation scales on visible data following a q 2 behavior and is temperature-dependent. Such temperature dependence is found in a good agreement with that measured at lower q, suggesting that its origin is mainly due to a dynamic attenuation mechanism. The comparison between the present data with those obtained by Inelastic X-ray Scattering suggests the existence of a cross-over to a different attenuation regimes. Our present understanding of the sound attenuation mechanisms in vitreous systems is poor compared to that of crystalline materials although this topic has attracted the interest of several researchers from both experimental and theoretical points of view [1]. In particular, the nature of vibrational dynamics of disordered systems, as derived from the study of the "low-frequency" excitations (in the hypersonic range), has been a highly debated subject in the last years [2,3,4,5,6]. Vitreous silica (v-SiO 2 , or amorphous quartz) has been extensively studied as prototype of a strong glass. Nevertheless, the experimental results reported in literature had conflicting and controversial interpretations [7,8,9,10,11]. To achieve an overall characterization of this particular system is crucial to understand the vibrational dynamics of the vitreous state. It is well known that a plane wave excitation can propagate freely in a disordered structure only when the wavelength is much greater than the scale spanned by microscopic inhomogeneities. As the wavelength shortens the wave is attenuated, distorted, and scattered with increasing magnitude. As a matter of fact, the waves can even become over-damped when the wavelength approaches the interparticle spacing and the excitations become more directly affected by the microscopic disorder characteristic of the glass structure. The question about the nature of excitations far from the long wavelength limit, is unlikely to have a single answer [12,13,14]. Indeed different mechanisms have been suggested in order to explain the attenuation of an acoustic plane wave excitation namely: attenuation induced by topological disorder, thermally activated processes, anharmonic effects, two-level systems (TLS) processes [15]. In general, anharmonic effects are particularly relevant at relatively high temperatures while the importance of the two-level systems is confined at very low temperatures (T < 5 ÷ 10 K). In the intermediate range 10 K < T ≪ T g the TLS effects are not important and disordered induced mechanisms, thermally activated processes and anharmonic effects play the most important role in acoustic attenuation. Anyway, sound propagates through glasses and longitudinal and transverse phonons are found to be still well defined at relatively large wave-vectors (up to 5 nm −1 ) with a linear relationship between frequen...

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“…And a similar change in g OO ðrÞ from LDA to HDA is also found [57]. A theoretical study [58] shows that the boson peaks at different conditions can be rescaled to one master curve with a characteristic energy E c in the following way:…”

mentioning

confidence: 58%

Pressure Effect on the Boson Peak in Deeply Cooled Confined Water: Evidence of a Liquid-Liquid Transition

et al. 2015

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The boson peak in deeply cooled water confined in nanopores is studied to examine the liquid-liquid transition (LLT). Below ∼180 K, the boson peaks at pressures P higher than ∼3.5 kbar are evidently distinct from those at low pressures by higher mean frequencies and lower heights. Moreover, the higher-P boson peaks can be rescaled to a master curve while the lower-P boson peaks can be rescaled to a different one. These phenomena agree with the existence of two liquid phases with different densities and local structures and the associated LLT in the measured (P, T) region. In addition, the P dependence of the librational band also agrees with the above conclusion. DOI: 10.1103/PhysRevLett.115.235701 PACS numbers: 64.70.Ja, 25.40.Fq, 63.50.-x Water is a continuing source of fascination to scientists because of its abnormal behavior at low temperatures T. Upon cooling, its thermodynamic properties, such as density, isobaric heat capacity, and isobaric thermal expansivity, deviate from those of simple liquids significantly [1][2][3][4]. In addition, glassy water, also called amorphous ice, exhibits polyamorphism. Experiments show that two kinds of amorphous ice, low-density amorphous ice (LDA) and high-density amorphous ice (HDA), exist at very low temperatures [5][6][7]. These two phases can transform to each other through a first-order-like transition [7,8]. To account for these mysterious phenomena, a "liquid-liquid critical point (LLCP)" scenario, which assumes a first-order low-density liquid (LDL) to high-density liquid (HDL) phase transition in the deeply cooled region of liquid water, has been proposed [9]. Therefore, experimental tests on the existence of the LDL and the HDL and the associated liquid-liquid transition (LLT) are important for understanding water. Nevertheless, such measurements are practically difficult due to the rapid crystallization of bulk water below the homogeneous nucleation temperature (235 K at 1 atm). To overcome this barrier and enter the deeply cooled region of water, different systems, including aqueous solutions [10][11][12][13][14], microsized water droplets [15], and confined water systems [16][17][18][19], have been prepared and studied. Particularly, when confined in a nanoporous silica matrix, MCM-41, with a 15-Å pore diameter, water can be kept in the liquid state at least down to 130 K [20,21]. Thus, the MCM-41-confined water system provides a chance to explore the hypothetical LLT.Recently, we observed a likely LLT in heavy water confined in MCM-41 by a density measurement. The associated phase diagram is shown in Fig. 1(a) [22]. However, the relevant measurements on the dynamic properties are still lacking. In fact, various dynamic properties, including the structural relaxation [10,16], the stretching vibration [10,11], the mean square displacement [23], etc., have been measured to study the phase behaviors of aqueous solutions or confined water. Examinations of FIG. 1 (color online). (a) Phase diagram of deeply cooled confined heavy water [22]. The inset shows th...

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Phonon interpretation of the ‘boson peak’ in supercooled liquids

Cited by 330 publications

References 30 publications

Heat capacity, Raman, and Brillouin scattering studies of M2O–MgO–WO3–P2O5 glasses (M=K,Rb)

Heat capacity, Raman, and Brillouin scattering studies of M2O–MgO–WO3–P2O5 glasses (M=K,Rb)

Sound attenuation in a unexplored frequency region: Brillouin ultraviolet light scattering measurements inv−SiO2

Pressure Effect on the Boson Peak in Deeply Cooled Confined Water: Evidence of a Liquid-Liquid Transition

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