Contribution of the terahertz vibrations to the high-temperature thermal conductivity of vitreous silica

Abstract

A combined inelastic X-ray and neutron scattering experiment is performed on the prototypical glass vitreous silica. The complementarity of the two techniques is exploited to determine the dynamic structure factor in a wide range of energies and wavevectors. The vibrational-mode spectral density is then used to compute the high-temperature thermal conductivity. The acoustic-like modes persisting at THz frequencies are shown to represent a relevant heat conduction channel, although they cannot account for the entire thermal conductivity.

Keywords:

• boson peak
• thermal transport
• amorphous solids
• X-ray scattering
• neutron scattering

Acknowledgements

G.B. is indebted to Prof. U. Buchenau for many fruitful discussions on the thermal conductivity in amorphous solids. C. Henriquet is kindly thanked for support in the preparation of the high-temperature set-up for the IXS experiment. We thank A.J. Dianoux for his help during the neutron experiments. E.F. thanks M.M. Koza for his support in the treatment of the neutrons data. Technical and financial support from the ILL facility is gratefully acknowledged.