Raman scattering investigation of the boson peak in a sodium silicate glass

Raman scattering is used to investigate the vibrational spectrum of a sodium silicate glass around the boson peak frequency range at temperatures between 10 and 450 K. A comparison with the density of states measured with coherent neutron scattering allows one to determine the Raman coupling function. This quantity presents a linear frequency dependence in the boson peak region and a negligible temperature dependence, confirming similar observations in other glasses. The Raman spectra at different temperatures scale according to the Debye frequency determined from the sound velocity measured at terahertz frequency with inelastic X-ray scattering. This result confirms previous neutron scattering data and the importance of measuring the elastic properties of the glass in the proper frequency range.