regime $T > T_Q$ - thermal conductivity

theory - 1949 Kittel

1951 Klemens

• *Why? —- Klemens - Thermal conductivity - Transverse for high temperatures, while longitudinal for low temperatures *

R. Berman 1951 Solids at Low Temperatures (Experimental) -The Thermal Conductivities of Some Dielectric Solids

Birch-Clark 1940 and particularly theory - Part 2

1987 Thermal conductivity of amorphous solids above the plateau David G. Cahill and R. O. Pohl

we find above —50 K a magnitude and temperature
dependence which agrees with the model of the minimum
thermal conductivity proposed by Slack. In the limit of
high temperatures, this model leads to a phonon mean
free path equal to the interatomic spacing as first noted in
glasses by Birch and Clark and by Kittel.