On the existence of Einstein oscillators and thermal conductivity in bulk metallic glass

Low-temperature specific heat and thermal conductivity of bulk metallic glasses are measured to identify the primary vibrational modes associated with their unique structures. An Einstein-type localized vibrational mode with an Einstein temperature of 112K is found in bulk metallic glass Ni59.5Nb33.6Sn6.9. This localized vibrational mode causes resonant scattering of phonons and results in the localization of phonons which leaves the phonon hopping conduction the limiting mechanism of thermal transport in bulk metallic glass Ni59.5Nb33.6Sn6.9 at high temperature.