Non-Debye normalization of the glass vibrational density of states in mildly densified silicate glasses

Abstract

The evolution of the boson peak with densification at medium densification rates (up to 2.3%) in silicate glasses was followed through heat capacity measurements and low frequency Raman scattering. It is shown that the decrease of the boson peak induced by densification does not conform to that expected from a continuous medium; rather it follows a two step behaviour. The comparison of the heat capacity data with the Raman data shows that the light-vibration coupling coefficient is almost unaffected in this densification regime. These results are discussed in relation to the inhomogeneity of the glass elastic network at the nanometre scale.

Boson peak as a probe of quantum effects in a glassy state of biomolecules: The case of L-cysteine

“…[5,6,[11][12][13][14] In general, the observed spectra exhibited a broad central line with a weak shoulder between 15 and 30 cm −1 . [11,12,15] Similar trend was also observed in specific heat data.…”

“…[11,12,15] Similar trend was also observed in specific heat data. [13,16] The C/T 3 against T plot presented a low temperature (T ∼ 15 K) anomaly related to the BP . [13,16] Studies on short protein fragments such as amino acids could provide a very interesting approach to solve the problem.…”

“…[13,16] The C/T 3 against T plot presented a low temperature (T ∼ 15 K) anomaly related to the BP . [13,16] Studies on short protein fragments such as amino acids could provide a very interesting approach to solve the problem. The low molecular weighting amino acids are very suitable for computational modeling due to the comparatively small structures and can be used as functional prototypes of more complex structures such as proteins and lipids.…”

Structural heterogeneity and pressure-relaxation in compressed borosilicate glasses by in situ small angle X-ray scattering

“…Together, they describe the "distance from equilibrium" 4 of the considered glass 5 and, hence, its potential energy at real p and T. In a pragmatic consideration, they can be used to assess the system's thermomechanical history and resulting physical properties (e.g. molar volume, homogeneity, network topology, [6][7][8] and coordination 9,10 ), respectively, which were generated during freezing. Depending on the observation time, endothermal relaxation, and exothermal recovery, 11 respectively, occur towards real T and p. Thereby, p f and T f appear to relax simultaneously.…”

“…The state which is frozen-in during the glass transition can then be observed by enthalpy measurements as well as by compressibility measurements to assess residual and dynamic density and concentration fluctuations. In the present work, to investigate the compressibility variation with fictive pressure for a representative sodium borosilicate glass, 6,10 we are employing two experimental methods: Synchrotron small angle X-ray scattering (SAXS) and evaluation of the Landau-Placzek ratio (LPR). SAXS intensity extrapolated to very low angular regimes (q = 0) is directly related to compressibility.…”