$1K= 2 *10^{10} Hz$
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)