The origin of the anomalous low-frequency vibrational behaviour of amorphous solids

Abstract

The anomalous vibrational behaviour exhibited by non-crystalline materials - a peak in the vibrational density of states, and in the Raman spectrum (the boson peak) at low frequencies, and a peak in the heat capacity and a plateau in the thermal conductivity at low temperatures - is ascribed ta phonon localization associated with the strong scattering of phonons by density-fluctuation domains in the structure. Within such domains, short-range and medium-range arder is maintained, and outside them the material is structurally homogeneous and isotropie. This model can also explain the correlation between the boson-peak frequency and the position of the first sharp diffraction peak in the structure factor observed in a number of inorganie and polymerie amorphous solids.