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

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.