Temperature broadening of vibrational lines in glasses

The shape of vibrational lines and the temperature dependences of their width for structures with short-range and medium-range orders in oxide glasses have been studied. The relationship describing the contour of the line associated with internal vibrations of glass-forming polyhedra is derived in the framework of the model for deformation broadening of the vibrational spectra of two-level systems. It is found that the line within the width is represented by a Lorentzian contour, and the line wings decay as (ω − ω0)−4. It is demonstrated that a similar contour is observed for the lines corresponding to the intrinsic vibrations of clusters with hinged bonds, which form the boson peak. The shape of the line at 806 cm− for vitreous boron oxide, which is calculated in the framework of the proposed model, is in complete agreement with the experimental data in the temperature range 80–1900 K.