We present a simple phenomenological model for glasses which fits both the thermal conductivity κ and the specific heat C up to roughly 100 K. This includes the plateau in κ as well as the maximum in C/$T^3$ which occur between 3–10 K. In addition to conventional tunneling systems and Rayleigh scattering, we introduce a sharp increase in the density of states due to local excitations. This feature is consistent with both Raman and neutron scattering. The absence of these states at low frequencies is due to interactions between the local modes and phonons.

• Received 16 July 1987

DOI:https://doi.org/10.1103/PhysRevB.36.7620