Istituto dei materiali per l'elettronica ed il magnetismo     
Orsingher L., Fontana A., Gilioli E., Carini G. J., Carini G., Tripodo G., Unruh T., Buchenau U. Vibrational dynamics of permanently densified GeO2 glasses: Densification-induced changes in the boson peak. In: Journal of Chemical Physics, vol. 132 (12) article n. 124508. American Institute of Physics, 2010.
Vitreous GeO2, one of the main prototypes of strong glasses, was densified at several pressures up to 6 GPa, achieving more than 20% of densification. The density dependence of the vibrational density of states and of the low temperature properties of these glasses was investigated by means of inelastic neutron scattering and calorimetric measurements. With increasing density, both the boson peak and the bump in c(p)/T-3 versus T plot exhibit variations which are stronger than the elastic medium expectation. If one reduces the measured spectra to a common master curve, one finds that this is only possible for the densified samples; the first densification step has an additional effect, similar to other cases in the literature. Nevertheless, the existence of a master curve for the three densified samples proves that the total number of excess modes remains constant on further densification. The experimental data are discussed in the framework of different theoretical models.
DOI: 10.1063/1.3360039
Subject boson systems
germanate glasses
high-pressure effects
neutron diffraction
specific heat
vibrational modes
vitreous state

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