On the role played by bending vibrations in heat transfer in layered crystals

The temperature dependences of the thermal conductivity of layered crystals (LCs) of graphite, boron nitride, gallium sulfide, etc., are analyzed. It is shown that the bending branch of vibrations typical of LCs determines the behavior of the thermal conductivity only in the region of its increase. The decrease in thermal conductivity upon heating cannot be explained by taking into account the bending vibrations only, and phonon-phonon interaction processes become effective only in the case of excitation of other branches in the acoustic spectrum.