Model of defect diffusion and development of the boson peak in an amorphous solid

A schematic model is proposed for understanding the boson peak as a consequence of the coupling between slowly decaying density fluctuations and the transverse sound modes that develop in the amorphous solid. The present analysis demonstrates that the nature of the dynamics of defect densities in the disordered system plays a crucial role for the appearance of the peak. We compare the results for the dynamic structure factor with the scattering data of Sokolov et al. [J. Non-Cryst. Solids 172-174, 138 (1994)]. With the relaxation time for the defects becoming longer which is the case more appropriate for the strong glasses as compared to the fragile glasses where structural degradation occurs more easily, the boson peak become more pronounced.