Relaxing local modes and the theory of low-frequency Raman scattering in glasses

Raman scattering in glasses is investigated theoretically. The experimental Raman spectra of glasses exhibit a low-frequency peak (at ∼10 cm−1) that, as a rule, is attributed to vibrational modes of nanometer-sized structural units (nanocrystallites). It is established that the elastic moduli of nan...

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Bibliographic Details
Published in:Physics of the solid state 2003-05, Vol.45 (5), p.830-837
Main Authors: Bondarev, V. N., Zelenin, S. V.
Format: Article
Language:English
Subjects:
Distribution functions
Modulus of elasticity
Nanocrystals
Pressure effects
Raman spectra
Size distribution
Surface tension
Vibration mode
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Summary:Raman scattering in glasses is investigated theoretically. The experimental Raman spectra of glasses exhibit a low-frequency peak (at ∼10 cm−1) that, as a rule, is attributed to vibrational modes of nanometer-sized structural units (nanocrystallites). It is established that the elastic moduli of nanocrystallites must necessarily be dependent on their sizes due to the Laplace pressure effect. A theory of the low-frequency peak is constructed using a realistic size distribution function of nanocrystallites with allowance made for the Laplace pressure effect and the dissipation of vibrational energy. Within this theory, the shape of the low-frequency peak and its evolution with temperature can be analyzed quantitatively. The proposed approach offers a physical interpretation of the experimental data and provides insight into the relation of the characteristic nanocrystallite sizes to the elastic moduli and surface tension coefficients of materials.
ISSN:1063-7834
1090-6460
DOI:10.1134/1.1575319