THE EFFECTIVE FREE-PATH LENGTH OF PHONONS IN DIAMOND

The influence of normal (N) processes of phonon-phonon interactions on the temperature dependence of the effective free path length l(eff) of phonons in diamond was considered in the limits of Callaway's theory. It was shown that in perfect crystals at low temperatures N processes prevail over all other types of scattering and that even in the range of room temperature they play a significant role. In connection with this the possibility of second sound spreading in diamond was considered together with the specific influence of crystal boundaries on l(eff). It was shown that in diamond with a reduced content of C-13 isotope it is possible to reveal a state corresponding both to the Knudsen minimum and to phonon flow close to the Poiseuille one.