The temperature dependence of the phononic band gap of NaI

Abstract

The position and size of the energy gap in the phonon density of states of NaI single crystal have been investigated by inelastic neutron scattering in a wide range of temperatures from 10 to 700 K. The results reveal a pronounced temperature effect which effectively leads to closure of the phonon gap at temperatures in the range of 700–800 K. The results are discussed in the context of studies of possible intrinsic localized modes in the phonon gap of alkali halides.