High frequency acoustic modes in vitreous Beryllium Fluoride probed by inelastic X-ray scattering

TL;DR

This study uses inelastic X-ray scattering to observe high frequency acoustic modes in vitreous Beryllium Fluoride, revealing their dispersion and similarities with other network glasses, advancing understanding of glass dynamics.

Contribution

First observation of well-defined high frequency acoustic modes in vitreous BeF2 using inelastic X-ray scattering, highlighting their dispersion and similarities with other glasses.

Findings

High frequency acoustic modes are well-defined in vitreous BeF2.

Mode energy and linewidth disperse as Q and Q^2, respectively.

Results align with low-frequency sound velocity and absorption data.

Abstract

Inelastic X-ray Scattering measurements of the dynamics structure factor have bene performed on vitreous Beryllium Fluoride ({\it v-}BeF$_2$) at $T$=297 K in the momentum transfer, $Q$, range $Q$=1.5$\div$10 nm$^{-1}$. We find evidence of well defined high frequency acoustic modes. The energy position and linewidth of the excitations disperse with $Q$ as $\propto Q$ and $\propto Q^2$, respectively up to about one half of the first maximum of the static structure factor. Their magnitude compare favorably with low-frequency sound velocity and absorption data. The results indicate worth mentioning similarities of the high frequency collective dynamics of different network forming glasses such as {\it v-}B$_2$O$_3$ and {\it v-}SiO$_2$.