Elastic properties of permanently densified silica: A Raman, Brillouin light, and x-ray scattering study

Zanatta, M.; Baldi, G.; Caponi, Silvia; Fontana, A.; Gilioli, E.; Krish, M; Masciovecchio, C.; Monaco, G.; Orsingher, L.; Rossi, F.; Ruocco, G.; Verbeni, R.

doi:10.1103/physrevb.81.212201

Cited by 55 publications

(96 citation statements)

References 38 publications

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“…It can been observed that I BP decreases with density, while ω BP increases with density. Both of these two trends (decrease of the intensity and increase of the frequency) have been observed experimentally in many system, such as in pure silica 80 , in lithium silicate glass 81 , in a Na 2 FeSi 3 O 8 glass 82 as well as in different polymers 83 .…”

Section: Boson Peakmentioning

confidence: 92%

Structural, vibrational, and thermal properties of densified silicates: Insights from molecular dynamics

Bauchy

2012

The Journal of Chemical Physics

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Structural, vibrational and thermal properties of densified sodium silicate (NS2) are investigated with classical molecular dynamics simulations of the glass and the liquid state. A systematic investigation of the glass structure with respect to density was performed. We observe a repolymerization of the network manifested by a transition from a tetrahedral to an octahedral silicon environment, the decrease of the amount of non-bridging oxygen atoms and the appearance of three-fold coordinated oxygen atoms (triclusters). Anomalous changes in the medium range order are observed, the first sharp diffraction peak showing a minimum of its full-width at half maximum according to density. The previously reported vibrational trends in densified glasses are observed, such as the shift of the Boson peak intensity to higher frequencies and the decrease of its intensity. Finally, we show that the thermal behavior of the liquid can be reproduced by the Birch-Murnaghan equation of states, thus allowing us to compute the isothermal compressibility.

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Section: Boson Peakmentioning

confidence: 92%

Structural, vibrational, and thermal properties of densified silicates: Insights from molecular dynamics

Bauchy

2012

The Journal of Chemical Physics

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“…In some systems, 14,18,19 it appears that the BP variation is solely associated with the change in the Debye frequency, which accounts for the modifications of the elastic continuum medium. In other cases, 13,[15][16][17] the BP shifts more strongly than suggested by the simple variation of the macroscopic medium. Specifically, this second behavior is observed when the system is subjected to an important volume change, of the order of 10% to 20%.…”

Section: Introductionmentioning

confidence: 96%

“…Among them we may recall the soft potential model, 4 the mode-coupling theory applied to the vibrations in glasses, 5 models on a lattice 6 or on the continuum 7 with randomly fluctuating elastic constants, and harmonic models where the atoms vibrate around topologically disordered configurations. 8,9 Experimentally the BP has been studied as a function of macroscopic parameters such as the temperature, 10,11 the density, [12][13][14][15] and the pressure 16,17 or during chemical vitrification 18 or as a function of the quenching rate. 19 It is observed that the BP shifts to higher frequencies and decreases in intensity when the pressure or the density is increased.…”

Section: Introductionmentioning

confidence: 99%

Elastic anomalies at terahertz frequencies and excess density of vibrational states in silica glass

2011

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We study the temperature dependence of acousticlike excitations measured by means of inelastic x-ray scattering at terahertz frequencies in silica glass. The apparent sound velocity shows, between 300 and 1600 K, the same temperature variation measured, at lower frequencies, by Brillouin light scattering. On the contrary the vibrations at the boson peak (BP) present a much stronger temperature dependence, as indicated by neutron scattering data. The measured dispersion and damping are used to compute the contribution to the vibrational density of states (VDOS) coming from the propagating acousticlike modes. This part of the VDOS accounts only for a fraction of the BP intensity, indicating that other kinds of excitation accumulate in this frequency range. It is consequently not surprising that the BP does not follow the temperature evolution of the Debye frequency, which describes the modification of the continuum medium. Finally we present a comparison between the experimentally accessible quantities and a recently proposed model for the vibrations in glasses, based on the assumption of random spatial variations of the shear modulus [Schirmacher, Europhys. Lett. 73, 892 (2006)].

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“…Moreover, both theoretical and experimental studies assign the boson peak in glass to a phenomenon reminiscent of the van Hove singularity of the transverse phonon of the crystal counterpart [33,42,43]. It is worth mentioning that the boson peak has a dependence on the density of the material: as the density increases, the frequency of the boson peak increases and the height decreases [29][30][31]35,37,44]. Then, considering that the order parameter of the hypothetical LLT is just the density [9], the boson peak provides a good way to examine the existence of the LLT.…”

mentioning

confidence: 99%

“…Data were reduced by DAVE [26]. The boson peak is a broad peak observed at frequencies ∼2-10 meV in the inelastic neutron [27][28][29][30][31], nuclear inelastic [32][33][34][35], and Raman [36][37][38][39] scattering spectra of disordered materials and supercooled liquids. Its origin is widely believed to be related to the transverse dynamics of the material [32][33][34]40,41].…”

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confidence: 99%

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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Elastic properties of permanently densified silica: A Raman, Brillouin light, and x-ray scattering study

Cited by 55 publications

References 38 publications

Structural, vibrational, and thermal properties of densified silicates: Insights from molecular dynamics

Structural, vibrational, and thermal properties of densified silicates: Insights from molecular dynamics

Elastic anomalies at terahertz frequencies and excess density of vibrational states in silica glass

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

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