Equivalence of the Boson Peak in Glasses to the Transverse Acoustic van Hove Singularity in Crystals

We compare the atomic dynamics of the glass to that of the relevant crystal. In the spectra of inelastic
scattering, the boson peak of the glass appears higher than the transverse acoustic (TA) singularity of the
crystal. However, the density of states shows that they have the same number of states. Increasing pressure
causes the transformation of the boson peak of the glass towards the TA singularity of the crystal. Once
corrected for the difference in the elastic medium, the boson peak matches the TA singularity in energy
and height. This suggests the identical nature of the two features.