The results show that additional harmonic excitations coexist with sound waves below 1 THz, and that these excitations correspond to relative rotation of SiO~ tetrahedra.
B. Ruffl´e, D.A. Parshin, E. Courtens, and R. Vacher
In conclusion, it clearly appears that acoustic modes alone are not able to account for observations on most glasses in the THz range. The acoustic modes are merely a subset of all the low frequency vibrations in disordered systems. QLVs predicted by the soft potential model take these into account using parameters that are determined fully independently by two-level-system measurements
Summing up, on the basis of Fig. 1(b) one can conclude
that (i) no correlation exists between EIR and EBP, and
(ii) the Ioffe-Regel limit for almost all the investigated
glasses lies above the boson peak position.
$1K= 2 *10^{10} Hz$
https://www.unitsconverters.com/en/Hertz-To-Kelvin/Unittounit-3511-3514?MeasurementId=15&From=3511&To=3514
$1 THz \approx 50K$
$1K \approx 0.08 meV $
https://www.unitsconverters.com/en/Hertz-To-Kelvin/Unittounit-3511-3514?MeasurementId=15&From=3511&To=3514
## Buchenau
1998 [Sound scattering in silica](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5439/PhysRevB.57.2663.pdf)
1992 [Soft localized vibrations in glasses and undercooled liquids](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5492/buchanau.pdf) U. Buchenau
> An explanation for their localization is
1986 [Low-frequency modes in vitreous silica](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5495/buchnau%2B1986.pdf)
> The results show that **additional harmonic excitations coexist with sound waves below 1 THz**, and that these excitations correspond to relative rotation of SiO~ tetrahedra.
## Angell [Boson peaks and floppy modes: some relations between constraint and excitation phenomenology, and interpretation, of glasses and the glass transition](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5489/angell.pdf)
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.75.024201
2013 [The Boson peak in supercooled water](https://www.nature.com/articles/srep01980) Pradeep Kumar
## [The Boson Peak and its Relation with Acoustic Attenuation in Glasses](https://arxiv.org/pdf/0711.0461.pdf) B. Ruffl´e
B. Ruffl´e, D.A. Parshin, E. Courtens, and R. Vacher
> In conclusion, it clearly appears that **acoustic modes alone are not able to account** for observations on most glasses in the THz range. The acoustic modes are merely a subset of all the low frequency vibrations in disordered systems. **QLVs predicted by the soft potential model** take these into account using parameters that are determined fully independently by two-level-system measurements
[comment](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5542/ruocco.pdf) by Ruocco
> Summing up, on the basis of Fig. 1(b) one can conclude
> that (i) no correlation exists between EIR and EBP, and
> (ii) the Ioffe-Regel limit for almost all the investigated
> glasses lies above the boson peak position.
reply - https://coulomb.umontpellier.fr/perso/benoit.ruffle/2007_98_PhysRevLett_Ruffle.pdf
## [Glass-Specific Behavior in the Damping of Acousticlike Vibrations](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5485/ir%2Bis%2Bbp.pdf)
B. Ruffle´, G. Guimbretie`re,1 E. Courtens,1 R. Vacher,1 and G. Monaco
> An analysis of literature results reveals that the boson-peak frequency is closely related with a
> Ioffe-Regel limit for sound in many glasses
> [ An analysis of literature results reveals that the boson-peak frequency is closely related with a Ioffe-Regel limit for sound in many glasses.](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5485/ir%2Bis%2Bbp.pdf)
